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1775-6.3.1, PLC-3 Programmable Controller Backup Systems, User

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1. 1775 SR Scanner 1775 S4A Scanner SELF SR TEST Pass C Ses PASS and FAIL indicators ASB 5 a Thumbwheel switch CH1 GH O 1 0 channel gns CHa a status indicators CH4 CH4 18750 Figure 6 3 f Indicator Locations for 1775 S5 and 1775 SR5 Scanner Modules 1775 SR5 Scanner 1775 S5 Scanner H SR 5 2 7 PASS PASS TO a PASS and FAIL indicators gt Fal S 5 a Thumbwheel switch O FORCE oa Forces enabled indicator el ate Q CH1 1 O channel S i ce amp che a status indicators CH4 XMTG Oan o O Q XMT Data Highway Data amp neyo a Highway Plus status RR amp ERR indicators 18751 6 5 Chapter 6 Diagnosing Faults Figure 6 4 Indicator Locations for 1775 MX Memory Communication Module 1775 MX Scanner FAIL O i PASS and FAIL indicators BU O a Status indicators 18752 Table 6 D 1 0 Channel Indicators for All Scanner Modules Indicator Status Description CHx Communication between scanner module and the I O chassis on the corresponding I O channel is properly established Configured for I O There is a fault on one or more of the I O chassis on the FLASHING Scanning corresponding I O channel No I O chassis are configured on the corresp
2. Figure 2 4 Location and Function of I O Chassis Backplane Switches Switch Last State ON Outputs of this I O chassis remain in their last state when a fault is detected by this I O adapter 1 Outputs of this I O chassis are turned off when a fault is OFF ON i OFF detected by this I O adapter lt a 2 i Switch 3 ag Processor Restart Lockout A Always On 2 ON The I O chassis can be restarted from 5 e the processor 6 a OFF The processor is locked out from A 7 restarting the I O chassis after a fault gt Always On 8 a Switches Addressing 5 6 O OFF OFF 2 slot Pressed in ON OFF 1 slot 2 at top Closed ON E OFF ON 1 2 slot 2 3 Pressed in at cH bottom Open OFF JL ON ON Not allowed NOTES 1 CAUTION If you set this switch to the ON position when a fault is detected outputs connected to this chassis remain in their last state to allow machine motion to continue We recommend that you set switch 1 to the OFF position to de energize outputs wired to this chassis when a fault is detected 2 The 1771 AS adapter does not support 1 slot or 1 2 slot addressing When you use this adapter set switches 5 and 6 to the OFF position 3 The 1771 ASB series A adapter does not support 1 2 slot addressing 16191 2 7 Chapter 2 Installing a Backup System Configuring Scanner M
3. TS oS as a TA Er En Era weze B S555 l Terminator Switch at Bottom Edge of Module 18754 Figure 2 8 Setting Backup Switches on 1775 S5 and 1775 SR5 Scanner Modules Not Used Not Used always UP always UP ON ON OFF Switch Positions UP Switch is away from board DOWN itch i 2 3 4 ON Switch is toward board OFF OFF 4 4 Set per Table 2 B 10975 1 Table 2 B Backup Switches for 1775 S5 and 1775 SR5 Scanner Modules Switch Switchover Method 2 3 Processor Automatic switchover with controllable DOWN UP both primary and backup switchback Automatic switchover with no DOWN UP primary switchback UP UP backup Manual switchover uP DOWN both primary and backup Stand alone mode up uP both primary and backup 2 10 Chapter 2 Installing a Backup System Selecting a Backup Cable Choose a backup cable for the switchover method desired Table 2 C lists the choices See Figure 2 9 through Figure 2 11 for wiring information Table 2 C Backup Cables Switchover Method Backup Cable Automatic switchover with no switchback 1775 CBA 1775 CBB 1775 CM2 Automatic switchover with controllable switchback Manual switchover 1775 CBB 1 Use for scanner backup configuration 2 Use for MX backup configuration Figure 2 9 Backup Cable Wiring for Scanner Back
4. Figure 2 1 Connections for a PLC 3 Backup System Using Scanner Backup 1 2 9 2 Y m 9 H alla io z H 8 s EE l 0 J 12 4 8 J o 8 o K j 8 o 909 i i i ao 10 To Earth 5 7 Ground 13 JE 3 a 11 o 3 R nn l s MS fe mS 3 4 8 S 8 7 fe O a To other 6 AJU D 6 NJU J 1 0 Chassis in the Channel Blue Shield LO 7 t O ce PLC 8 Processor Primary Power Supply cat no 1775 P1 Clear O 1771 I O Chassis cat no 1771 A1B A2B A3B A4B _ Power Supply cat no 1771 P2 Processor Chassis Power Cable 6ft cat no 1775 CAP I O Power Cable 1ft cat no 1771 CE Twinaxial Cable cat no 1770 CD 10 000 ft Max Each I O Channel at 57 6K Baud Terminator cat no 1770 XT Connect one at each end of the I O Channel PLC 3 Processor backup Backup Cable cat no 1775 CBA CBB Backup Communication Cable cat no 1770 CD Ground Bus Plate 13 Connection between Power Supply System Common studs ANODOaPWND oo o oo 10391 2 3 Chapter 2 Installing a Backup System
5. B22 1 05251 Source E2 2 1 0 2 0 0000000000000000 Boe Destin 0000000000000000 MOVE 6 10 Source 0000000000000000 S9 Destin 0000000000000000 Source 0000000000000000 S9 Destin 0000000000000000 Chapter 6 Diagnosing Faults 10988 1 Chapter 6 Diagnosing Faults 6 12 Keep the following points in mind when you use the fault routine in your ladder program the rung in the main routine must be executed in both the primary and backup processors you must make certain that the set value in the watchdog timer configuration is large enough to include the execution of this fault routine along with the normal program scan any logic which follows the RET instruction in the fault routine section will not be executed Interpreting the Saved Diagnostic Words Status word S9 0 stores the user program section number in bits 0 and 1 Table 6 1 shows how to interpret these bits The other bits which may be set in this word can be ignored Table 6 1 Program Section Bits Two Least Significant Ladder Program Section where Fault Bits in 9 0 Occurred 00 Fault not in ladder program 01 Main routine RM 10 Subroutine RS 11 Fault Routine RF Status word S9 1 saves the rung number which caused the major fault to occur By changing the data display on your programming device to decimal format you can identify the
6. Figure 2 2 Connections for a PLC 3 Backup System Using MX Backup 1 2 9 2 p Q gi Q l m Q M 8 6 Ls EE Ls EE I 12 J o 38 e R O 8 o 90 10 To Earth 5 7 j Ground 13 o 3 i 11 y 3 eed a Ul 3 Y 4 ey 4 S fe O 3 S g 8 _ To other 6 te A JU J 6 te JU J I O Chassis in the Channel e Blue Shield LO 7 t i O LO PLC 8 Processor Primary Power Supply cat no 1775 P1 Clear C 1771 I O Chassis cat no 1771 A1B A2B A3B A4B _ Power Supply cat no 1771 P2 Processor Chassis Power Cable 6ft cat no 1775 CAP I O Power Cable 1ft cat no 1771 CE Twinaxial Cable cat no 1770 CD 10 000 ft Max Each I O Channel at 57 6K Baud Terminator cat no 1770 XT Connect one at each end of the I O C
7. e HBa pem m o0 0000 o Fe HIB88 Terminator cat no 1770 XT Refer to page 2 23 Shield Twinaxial Cable cat no 1770 CD Gis Shield To other PLC 8 systems Clear Clear Channel No 1 Shown Channel No 1 Shown 10393 2 18 Chapter 2 Installing a Backup System If you designate another I O channel for use as a peer to peer communication channel replace the references to I O channel 1 with the actual I O channel used in the following procedure 1 Connect one end of a cat no 1770 CD twinaxial cable to the I O channel 1 terminals on the terminal swing arm of a scanner module in the backup processor If this is a 1775 S4A or 1775 SR scanner module do not connect the shield For 1775 S4A and 1775 SR scanner modules install a cat no 1770 XT terminator to the I O channel 1 terminals in the backup processor as shown in Figure 2 15 For 1775 S5 and 1775 SR5 scanner modules you can either install a 1770 XT terminator or select a terminator by using the internal switches as shown in Figure 2 17 on page 2 23 Important If the internal terminator option is used the link will be unterminated if the swing arm is removed from the scanner 2 Connect the other end of the 1770 CD twinaxial cable to the I O channel 1 terminals on the terminal swing arm of the corresponding scanner module in the primary processor Connect the shield Connect one end of another 1770 CD twinaxia
8. JMP 17 Source A S0 5 0000000000000000 Source B BO 1 0000000000000001 fs S0 4 S0 4 BESS ESS SESE SRS SSR SS SRS See SRS SS SSS ie Sse Sess U S aL 17 10983 1 Important When using rungs like those in Figure 5 4 be sure to disable the rungs before editing the program The PLC 3 does not calculate a checksum during on line editing but when on line editing is complete it recalculates the checksum You can re enable the rungs after editing is complete and you update the reference value 5 11 Chapter 5 Programming Techniques Refer to the PLC 3 Family Programmable Controller Programming Reference Manual publication 1775 6 4 1 for detailed information regarding the data table status section 5 12 Chapter 5 Programming Techniques 1775 MX Module Communication If the PLC 3 backup system uses memory communication modules there are additional bits in the data table status section file 4 word 0 to indicate communication status between memory communication modules Status information for the memory communication module resides in file 4 words 0 1 and 2 of the data table status section You can monitor the operation of a memory communication module by examining the contents in word 0 of status file 4 S4 0 Figure 5 5 and Table 5 B show the meaning of each bit of this word Figure 5 5 Status Information for the Memory Communication Module Status File 4 W
9. 4 28 Table 4 J Enable Compare If the memory communication module Then bit 13 is set in file 4 word 0 of the status section You must reset this bit The memory communication module continues the comparison until a miscompare occurs completes the program compare without error bit 12 is set in file 4 word 0 of the status section the address of the rung containing the miscomparison is put into file 4 words 1 and 2 and bit 14 is reset in file 4 word 0 encounters a miscompare LIST will show L Enable Program Compare A Disable Program Compare To continue the comparison you must reset the status bit bit 12 in file 4 word 0 and reselect ENABLE COMP For a further description of status bits see Using Data Table Status Bits in chapter 5 of this manual For a program comparison to occur the primary processor must be in run mode or test mode If you switch the primary processor to program mode the program comparison function becomes inactive When you switch the primary processor out of program mode program comparison will become active again To specify limits in the ladder program use the syntax shown below You can use either the slash or the comma as a delimiter between parameters ENABLE COMPARE M s f where mis the limit for the main program section s is the limit for the subroutine program section f is the limit for the fault program section Chapter 4 Using the 1775 MX Memory Co
10. Error Codes Table 4 K is a list of error codes These error codes may appear while you are controlling the operation of a memory communication module through message instructions from a ladder program Table 4 K Program Control Error Codes Error Code Description 1 Unknown command Ambiguous command Syntax errors that can 3 Invalid compare limits be detected when the 4 Unknown object instruction is enabled 5 Invalid data table section o gt Missing object Too many files in file list Program control is not enabled No communication between memory communication modules in primary and backup processors Commands not being sent by primary processor Processing errors that 1 Insufficient memory available in backup processor can occur while Continuous transfer was not stopped executing commands w Memory communication module cannot lock the backup system Memory communication module cannot unlock the backup system on File cannot be found or has zero length in primary processor Memory communication module cannot enable outputs 4 33 Chapter 4 Using the 1775 MX Memory Communication Module If an error occurs check the following If the backup processor is powered down or faulted due to a memory error communication between memory communication modules will be interrupted until the backup processor is functional again A broken communication cable between memory communication modules will
11. use the real time interrupt routine to scan a selected area of the program on a real time basis 5 1 Chapter 5 Programming Techniques Timers and Counters at Switchover 5 2 Using Repetition to Handle Short Input Pulses One method of handling short input pulses is to repeat the rungs that read those inputs For example if the duration of an input pulse is only 70 of the recommended time you could repeat rungs depending on this input at least twice in the program Put approximately one third of the program between the rungs Using Interrupts to Handle Short Input Pulses Another method of handling short input pulses is to use a real time interrupt routine to scan a selected area of the program on a real time basis For further information about this technique refer to the PLC 3 Family Programmable Controller Programming Reference Manual publication 1775 6 4 1 Special consideration must be given when timers and counters are being transferred from the primary processor to the backup processor Both timers and counters consist of three words The memory communication module transfers only one word at a time and a switchover could occur before all three words have been transferred One of the timer words contains the timer accumulator and another word contains the information used to maintain the accuracy of the timer Because the primary and backup hardware are asynchronous at switchover the accumulator may be increa
12. You may use either commas or slashes as delimiters when specifying files You can specify files like this SS fp Soho 83fgr ase r S1 tis or like this Ssf s2fp s3f3 Siefig where s is the data table section specifier Table 4 D fis the file number If the list of files contains a file that does not exist in the primary processor the memory communication module displays the message FILE LIST ERROR on the PLC 3 front panel or on the programming terminal proceeds to the next legitimate file in the list Chapter 4 Using the 1775 MX Memory Communication Module Table 4 1 Data Table Section Specifiers Data Table Selection Specifier Output Image Input Image Timer Counter Integer Floating Point Decimal BCD Binary B ASCII T c N F D High Order Integer Pointers Noj 0 I gt Status Important Timers and counters cannot be separated into control preset and accumulated value for the purpose of file transfers In addition pointers cannot be separated into section file and word Therefore no file number is necessary although you can specify file 0 For example to add the timer section to the fifth position in the list the counter section to the sixth position and the pointer section to the seventh position in the list type 5 Tor5 TO ENTER 6 C or 6 CO ENTER 7 P Or 7 PO ENTER Figure 4 3 shows a rung for executing
13. 5 Select automatic configuration to configure the I O channels in the backup processor 6 Manually configure peer to peer or backup communication channels if any are used If you need additional information to complete this step refer to the PLC 3 Family Programmable Controller Programming Reference Manual publication 1775 6 4 1 7 Turn off the backup processor 8 Turn on the primary processor 9 Select program load mode in the primary processor 10 Load the program into the primary processor 11 Select automatic configuration to configure the I O channels in the primary processor 12 Manually configure peer to peer or backup communication channels if any are used If you need additional information to complete this step refer to the PLC 3 Family Programmable Controller Programming Reference Manual publication 1775 6 4 1 13 Turn on the backup processor 14 Ifaseries A revision C or earlier communication adapter module 1775 KA is in the backup processor change the Data Highway station number now If you need additional information to complete this step refer to the section Programming Considerations for Data Highway and Data Highway Plus on page 5 13 or the PLC 3 Communication Adapter Module User s Manual publication 1775 6 5 2 15 Select run mode in the backup processor 16 Select run mode in the primary processor 3 2 Chapter 3 Operating a Backup System Startup Procedure Method 2
14. B EQ HQ HQ C EQ Q Ww w PR PR PR PR PR PR PR PR PR PR PR PR PR 1 2 3 0 3 SYSTEM CONFIGURATION FAULT MEMORY PARITY ERROR HARDWARE FAULT MAJOR I O FAULT WATCHDOG TIMEOUT BACKPLANE FAULT BUS I O DEACTIVE EXTENDER FAULT CONFIGURATION FAULT BACKUP CABLE FAULT BAD ADDRESS BAD INSTRUCTION STACK FAULT PR PR PR PR DETECTED AT RUNG RM S S9 1 DETECTED AT RUNG RS S S9 1 DETECTED AT RUNG RF S S9 1 NO FAULT DETECTED 6 13 Chapter 6 Diagnosing Faults Table 6 J Results The 1775 GA or 1775 S4B Procedure Will Display NO FAULT DETECTED lt major fault gt DETECTED AT RUNG RM lt number gt lt major fault DETECTED AT RUNG RS lt number gt lt major fault gt DETECTED AT RUNG RF lt number gt If the Processor Detects No fault A fault in the main program section A fault in the subroutine program A fault in the fault routine program A fault that does not generate a rung reference lt major fault gt 6 14 ALLEN BRADLEY WOU 94 ROCKWELL INTERNATIONAL COMPANY With offices in major cities worldwid WORLD EUROPE MIDDLE HEADQUARTERS EAST AFRICA Allen Bradley HEADQUARTERS 1201 South Second Street Allen Bradley Europa B V Milwaukee WI 53204 USA Amsterdamseweg 15 Tel 414 382 2000 1422 AC Uithoorn Telex 43 11 016 Th
15. Data Table Section Specifier Oo Output Image Input Image Timer Counter Integer Floating Point Decimal BCD Binary ASCII High Order Integer Pointers Status wm vl T gt wo Of TH Z EO A Important You must use the slash as the delimiter separating the entry number from the data table section specifier For example to add decimal file 2 to the fourth position in the list type 4 D2 ENTER 4 8 Chapter 4 Using the 1775 MX Memory Communication Module Important Timers and counters cannot be separated into control preset and accumulated value for the purpose of file transfers In addition pointers cannot be separated into section file and word Therefore no file number is necessary although you can specify file 0 For example to add the timer section to the fifth position in the list the counter section to the sixth position and the pointer section to the seventh position in the list type 5 T or 5 TO ENTER 6 C or 6 CO ENTER 7 P Or 7 P0 ENTER Important Changes to the file list do not become effective until you reselect the FILE TRANSFER function This helps prevent deleting a file by mistake To delete a file use the following procedure 1 To delete the third file for example type 3 ENTER 2 Move back to the MCM OPERATION menu by pressing ENTER 3 To make the change effective type 2 ENTER Now the third file on the file list has been deleted there is
16. 8 Turn on the primary processor 9 Select program load mode in the primary processor 10 Verify that channel configurations values in data tables and user program are correct in the primary processor If there are any incorrect entries correct them before proceeding 11 Turn on the backup processor 12 Select run mode in the backup processor 13 Select run mode in the primary processor 3 6 Chapter 3 Operating a Backup System Restart Procedure Method 2 1 For the scanner backup configuration place the switch located in the backup cable so that the processor currently controlling outputs is the primary processor 2 Reconnect the following cables a For scanner backup configuration reconnect the backup cable to the number one scanner module in the repaired processor b For the MX backup configuration reconnect the communication cables to the RCVG and XMTG connectors on the memory communication module in the faulted processor 3 Reconnect the terminal swing arms to all scanner modules in the repaired processor 4 Turn on the repaired processor 5 Check the configuration of each I O channel values in the data tables and the program in the repaired processor If there are any incorrect entries correct them before proceeding Manually reconfigure the repaired processor if necessary 6 Select run mode in the repaired processor Restart Procedure Method 3 1 Reconnect the backup cable to th
17. A Disable Program Compare To continue the comparison you must reset the status bit bit 12 in file 4 word 0 and reselect ENABLE PROG COMP For a further description of status bits see Using Data Table Status Bits in chapter 5 of this manual For a program comparison to occur the primary processor must be in run mode or test mode If you switch the primary processor to program mode the program comparison function becomes inactive When you switch the primary processor out of program mode program comparison will become active again if the selection ENABLE PROG COMP is still active in LIST Important Some data appearing in the ladder diagram is actually contained in the data table If you alter a ladder diagram in either the primary or the backup processor in such a way that the information in the data table changes but the information in the program section remains unchanged then the program comparison function will not detect a miscomparison This may happen when using the following instructions message send diagnostic detect block transfer timers file instructions counters bit shifts first in first out FIFO 4 13 Chapter 4 Using the 1775 MX Memory Communication Module 4 14 Disable Program Compare Command The DISABLE PROG COMP command lets you disable the program comparison function When this command is active the memory communication module resets the program comparison status bit
18. I O Cables Terminate at Terminal Swing Arms QO Line 1 Line 1 Channel Shield Shield Channel No 3 i No 4 Line 2 CN Line 2 Line 1 C3 Line 1 Channel f i Channel Nie Shield Shield re Line 2 C Line 2 10044 Important For 1775 S4A or SR scanner modules used as the number one scanner when using I O channel 5 to communicate with a peripheral device I O channel 4 of the number one scanner module cannot be used Do not make any connections to I O channel 4 2 15 Chapter 2 Installing a Backup System Connecting I O Communication Channels Figure 2 14 shows the connections when using I O channel 1 Figure 2 14 Connections for I O Communication Primary Processor Backup Processor Tne Ea Blue Terminator cat no 1770 XT Refer to page 2 23 Shield e Q Shield Twinaxial Cable cat no 1770 CD Q O O Q Channel No 1 Shown EEV To I O Chassis O Clear O Channel No 1 Shown Clear 10392 2 16 Chapter 2 Installing a Backup System If you designate another I O channel for use as an I O communication channel replace the references to I O channel 1 with the actual I O channel in the following procedure 1 Connect one end of a 1770 CD twinaxial cable Belden 9463 to the T O chann
19. I O Power Cable 1ft cat no 1771 CE 5 Twinaxial Cable cat no 1770 CD 10 000 ft Max Each I O Channel at 57 6K Baud 6 Terminator cat no 1770 XT Connect one at each end of the I O Channel 7 PLC 3 10 Processor backup 8 Backup Cable cat no 1775 CBA CBB 9 Backup Communication Cable cat no 1770 CD 10 Ground Bus Plate 18756 2 5 Chapter 2 Installing a Backup System Power Supply Considerations Grounding Considerations Shielding Considerations 2 6 For a PLC 3 backup system it is important to choose suitable power supplies and make sure they are connected properly To reduce the chance of inadvertent shutdowns due to loss of power we recommend using two separate 1775 P1 or P3 power supplies Use one power supply for the primary processor and the other power supply for the backup processor Further connect each power supply to a separate source of AC power Important In backup systems never use the processor supply for powering an I O chassis A processor failure could cause the I O to fail also For detailed information about installing power supplies refer to the PLC 3 Programmable Controller Installation and Operation Manual publication 1775 6 7 1 All grounding requirements applicable to a stand alone PLC 3 or PLC 3 10 processor also apply to backup systems In addition you need to do the following When using a 1775 P1 power supply connect the system common studs together o
20. Word 0 in the Data Table Bit Meaning 00 On when the backup processor is in the run mode 01 On when the backup processor is in the test mode 02 On when the backup processor is in the program mode 03 On when the backup processor is faulted 04 On when the backup processor has its outputs enabled 05 On when the backup processor is locked 06 On when the primary processor is locked 07 On when a communication error has occurred 10 On when backup to primary data transfer is enabled 11 On when LIST is controlling operation of the 1775 MX modules Off when the ladder program is controlling operation of the 1775 MX modules 12 On when the program compare function detects an error 13 On when the program compare function has successfully executed a complete pass 14 On when the program compare function is enabled Upon completing the program compare function the 1775 MX module sets either bit 12 or 13 to show the condition of the transferred data In order to check the status for the next program comparison you must reset these bits 15 On when a data table transfer is selected Off when a file transfer is selected 16 On when a continuous transfer is selected Off when a single transfer is selected 17 On when the 1775 MX modules are transferring data from the primary to the backup processor Bit 17 preconditions bits 15 and 16 5 14 Chapter 5 Programming Techniques Figure 5 6 Program Compare Status Informatio
21. ladder program the module cannot execute the LIST function selected the processor is in program load mode the MCM OPERATION menu displayed is for the memory communication module in the backup processor Note that there is an A entry for every L 4 5 Chapter 4 Using the 1775 MX Memory Communication Module The MCM OPERATION menu contains an entry for each LIST function listed in Table 4 D These functions are a subset of those available when using message instructions Table 4 D LIST Functions Command Description INACTIVE The memory communication module stops both continuous data transfers and continuous file transfers to the backup processor FILE TRANSFER The memory communication module transfers the selected files from the primary to the backup processor continuously FILE SE H ECTION Lets you select up to 16 files for use with the file transfer function DATA TABLE XFER The memory communication module continuously transfers the entire data table except the data table status section from the primary to the backup processor MEMORY DOWNLOAD The memory communication module stops any data transfer in progress and transfers the entire contents of PLC 3 memory from the primary to the backup processor LOCK SYSTEM The memory communication module has the edit resource for both the primary and backup processors This protects the ladder program in the current con
22. revision as their counterparts in the primary processor If not the backup system may not work properly 2 1 Chapter 2 Installing a Backup System 2 2 Important The number one scanner module thumbwheel set to 1 in both primary and backup processors must be a 1775 S4A or S5 for PLC 3 based processors or a 1775 SR or SR5 for PLC 3 10 based processors Figure 2 1 on page 2 3 shows typical connections for a PLC 3 backup system using scanner backup Figure 2 2 on page 2 4 shows typical connections for a PLC 3 backup system using MX backup Figure 2 3 on page 2 5 shows typical connections for a PLC 3 10 backup system using scanner backup Chapter 2 Installing a Backup System
23. 1 high state Reset 0 low state Channel configuration using LIST functions or message instructions to assign specific parameters to the I O channels on scanner modules Communication adapter module refers to the 1775 KA module used in PLC 3 and PLC 3 10 processors Memory communication module refers to the 1775 MX module used in PLC 3 processors Processor refers to a PLC 3 or PLC 3 10 programmable controller system consisting of a power supply chassis modules cables and all other components needed to achieve an operational system Programming terminal refers to an industrial terminal system e g Allen Bradley T4 T47 T50 or T60 terminals or an AT type computer with 6200 software Scanner module refers to 1775 S4A or S5 modules used in PLC 3 processors and or 1775 SR or SR5 modules used in PLC 3 10 processors Related Publications Preface For more information about components used with the PLC 3 backup system see the publications listed in Table B Table B Related Publications Publication Title Publication Number PLC 3 Programmable Controller Installation and Operation Manual 1775 6 7 1 PLC 3 Family Programmable Controller Programming Reference Manual 1775 6 4 1 1 0 Scanner Programmer Interface Module User s Manual 1775 6 5 2 PLC 3 Communication Adapter Module User s Manual 1775 6 5 1 1770 T4 Industrial Terminal System 1770 6 5 15 PLC 3 Family I O Scanner Communicati
24. 1 Turn off both the primary and backup processors if they are not already off 2 Turn on the primary processor Important Whichever processor you turn on first is designated as the primary processor the other is designated as the backup processor 3 Select program load mode in the primary processor 4 Load the program into the primary processor 5 Using the LIST functions in the primary processor configure all modules in the primary processor 6 Turn on the backup processor 7 Select program load mode in the backup processor 8 Using the LIST function perform a memory download Important If the primary processor was in run mode when you executed memory download the backup processor will be in run mode when the download is completed 9 Ifa series A revision C or earlier communication adapter module 1775 KA is in the backup processor change the Data Highway station number now If you need additional information to complete this step refer to the PLC 3 Communication Adapter Module User s Manual publication 1775 6 5 1 10 Select run mode in the backup processor 11 Select run mode in the primary processor Important You can write the ladder program so the primary processor automatically performs a memory download when it enters the run mode Doing this would allow you to skip step 8 in the startup procedure The example rungs in Figure 3 1 show how to program the download 3 3 Chapter 3 Operating
25. DISABLE COMPARE command the memory communication module disables the program comparison function and resets the program comparison status bit 4 29 Chapter 4 Using the 1775 MX Memory Communication Module Disable Outputs Command The DISABLE OUTPUTS command lets you inhibit the backup processor from taking control of outputs when the primary processor faults This command is useful during an on line editing session in an application where control of the outputs by the backup processor after switchover is undesirable while the programs are different When the primary processor executes a message instruction containing the DISABLE OUTPUTS command the memory communication module inhibits the backup processor from taking control of outputs when the primary processor faults Some conditions that influence the operation of this command are Ifthe primary processor is not in run mode the memory communication module disables the outputs of the backup processor regardless of your selection for the outputs Ifthe primary processor shuts down while the outputs are disabled the backup processor cannot take control of outputs Ifthe primary processor encounters a memory DOWNLOAD command while the DISABLE OUTPUTS command is executing the memory communication module temporarily enables the outputs of the backup processor At the conclusion of the memory download the outputs will be disabled To restore normal operation you must
26. Program Compare Limits Command The PROG COMP LIMITS command lets you select specific sections of the ladder program to be compared when ENABLE PROG COMP has been selected This function works in conjunction with the enable program compare function For the command to operate properly you must select the limit before you select ENABLE PROG COMP When you select PROG COMP LIMITS the PROG COMP LIMITS menu appears The menu shows the current value of limits used for the program compare function The first time you select this function all limits are set to zero The display will show the values of limits upon subsequent use Legitimate values for limits range from 1 to 32 767 PROG COMP LIMITS O COMP DISABLED AI 00000 SUBROUTINE 00000 FAULT 00000 ENTER NEXT gt Each limit has a corresponding label comment number in the ladder program If you need further assistance with label comment numbers refer to the PLC 3 Programmable Controller Programming Manual publication 1775 6 4 1 for detailed information When the enable program compare selection is active the memory communication module compares each section of the ladder program from the first rung through the specified rung As shown in LIST by 0 COMPARE DISABLED if you set the limit for a particular section at zero the module does not compare that section If the memory communication module cannot find the label comment number for a section it will compar
27. To guard against damage to equipment support 2 25 Chapter Objectives Starting Up a Backup System Operating a Backup System This chapter describes how to operate a backup system It recommends procedures for starting up a backup system shutting down a backup system restarting a backup system disconnecting a faulted processor restarting a repaired processor you follow the startup procedure recommended for your backup A CAUTION To guard against damage to equipment make sure system configuration If you use the wrong procedure the backup processor could be configured improperly or the primary processor could be prevented from regaining control of outputs To start up a backup system for the first time find the appropriate startup method for your backup configuration in Table 3 A then follow that procedure Table 3 A Startup Procedure Selection If You Have This Backup Configuration Scanner backup MX backup if programs in the primary and backup processors are different MX backup if programs in the primary and backup processor are identical Use This Startup Procedure Page Method 1 3 2 Method 2 3 3 3 1 Chapter 3 Operating a Backup System Startup Procedure Method 1 1 Turn off both the primary and backup processors if they are not already off 2 Turn on the backup processor 3 Select program load mode in the backup processor 4 Load the program into the backup processor
28. Using the 1775 MX Memory Communication Module 4 18 ENABLE COMPARE DISABLE COMPARE DISABLE OUTPUTS DIO ENABLE OUTPUTS LIST CONTROL PROGRAM CONTROL TRANSFER CONTROL STATUS ON STAT ON STATUS OFF STAT OFF Supported by series A release C or later 1775 MX modules Description The memory communication module compares a specified section of the ladder program in the backup processor with the corresponding section in the primary processor on a word by word basis The memory communication module prevents the execution of the program compare function The memory communication module inhibits the backup processor from taking control of outputs when the primary processor faults The memory communication module allows the backup processor to assume control of the outputs after switchover The memory communication module will be controlled by selections in LIST rather than by commands in message instructions of a ladder program The memory communication module will be controlled by commands in message instructions of a ladder program rather than the selections made in LIST The memory communication module forces a switchover from the primary to the backup processor The memory communication module enables data transfer from the backup processor to the primary processor The memory communication module disables data transfer from the backup processor to the primary processor To modify the operati
29. a Backup System Figure 3 1 Example Rung for Performing Memory Download at Startup Inputs B1 0 0 3 MSG JEN E Message 00 17 Control B0 0 DN Channel E2 14 1 Download 05 ER Shutting Down a Backup System Restarting a Backup System 3 4 To shut down a backup system do the following 1 Select program load mode in the primary processor 2 Select program load mode in the backup processor 3 Turn off the backup processor 4 Turn off the primary processor If you followed the shutdown procedure previously described you can restart the backup system by doing the following 1 Turn on the primary processor 2 Turn on the backup processor 3 Select run mode in the backup processor 4 Select run mode in the primary processor Chapter 3 Operating a Backup System Disconnecting To troubleshoot and or repair a faulted processor you may have to a Faulted Processor disconnect it To disconnect a faulted processor do the following 1 Turn off the faulted processor 2 Disconnect the following cables a For the scanner backup configuration disconnect the backup cable from the number one scanner module in the faulted processor b For the MX backup configuration disconnect the communication cables from the RCVG and XMTG connectors on the memory communication module in the faulted processor 3 Remove the terminal swing arms from all scanner modules in the faulted pro
30. a Bp pu D 0 U i x ic m U U I ic Oo Ae de UK Lith o ol _ E ki he o f l Terminator Blue cat no 1770 XT Refer to page 2 2 E Blue W page 2 23 O QO Twinaxial Cable cat no 1770 CD Shield ET QO D OR Shield nS gt e TRO Terminator 7 CHO OQ cat no 1770 XT GZO Clear Lix 7 Refer to page 2 23 Clear O eea Das Channel No 1 Shown Channel No 1 Shown 10394 2 21 Chapter 2 Installing a Backup System If you designate another I O channel for use as a backup communication channel replace the references to I O channel 1 with the actual I O channel used in the following procedure 1 Connect one end of a 1770 CD twinaxial cable to the I O channel 1 terminals on the terminal swing arm of a scanner module in the backup processor 2 For 1775 S4A SR scanner modules install a 1770 XT terminator to the I O channel terminals in the backup processor as shown in Figure 2 16 For 1775 S5 and SR5 scanner modules select a terminator by using the internal switches as shown in Figure 2 17 3 Connect the other end of the 1770 CD twinaxial cable to the I O channel 1 terminals on the terminal swing arm of the corresponding scanner module in the primary processor 4 For 1775 S4A SR scanner modules install a 1770 XT terminator to the I O channel terminals in the primary processor as shown in Figure 2 16 For 1775 S5 and SR5 scanner modules select a terminator by using the internal
31. against damage to equipment make sure Important Use of the commands STOP TRANSFER lt file list gt and START DATA is mutually exclusive You can use one and only one at a time Chapter 4 Using the 1775 MX Memory Communication Module Transfer Data Command The TRANSFER DATA command lets you transfer all sections of the data table except the status section from the primary processor to the backup processor one time only The transfer includes all sections of the data table except the status section section 13 The TRANSFER DATA command and the START DATA commands are quite similar The primary difference between them being that the TRANSFER DATA command causes the transfer to occur only one time whereas the START DATA command causes the transfer to occur continuously CAUTION To guard against damage to equipment make sure A there is sufficient memory available in the backup processor to accommodate the data table when the memory communication module 1775 MX executes a data table transfer If not enough memory is available the backup processor will shut down Important If you previously selected continuous data table transfer you must stop it before you can use the TRANSFER DATA command Use the STOP command to terminate a continuous data table transfer Download Command The DOWNLOAD command lets you transfer the entire contents of the PLC 3 memory from the primary processor to the backup processor This trans
32. cause both the primary and backup processors to fault fa memory error occurs while executing a memory download the memory communication modules will attempt to complete the download endlessly but without success 4 34 Chapter Objectives Signal Conditioning Programming Techniques This chapter describes techniques you can use to program a PLC 3 backup system In this chapter we describe input conditioning and timing requirements so switchover from primary to backup processor occurs as smoothly as possible recommendations for forcing I O executing block transfers using status bits and reducing backup communication overhead special considerations that apply when using communication adapter and memory communication modules To ensure that all rungs in the ladder program that read inputs read them correctly each input must remain in a steady state for at least the sum of input module delay time I O scan time program scan time This is the minimum recommended length of time during which an input should not change state Any input having a pulse of shorter duration may be missed by the primary backup or both processors There are several ways you can reduce the occurrence of missed inputs including use external circuitry to keep inputs in one state for the recommended length of time repeat rungs that read troublesome inputs as often as necessary in the ladder program to ensure accurate reads
33. load mode pass control to the backup processor cause a fault message to appear on the screen of a programming terminal if one is being used 6 1 Chapter 6 Diagnosing Faults Locating a Fault 6 2 Now the backup processor is controlling outputs If the backup processor attempts to execute the same logic rung that caused the primary processor to shut down the backup processor will display the message DEACTIVE on the front panel of the backup processor if a 1775 S4A or SR is scanner number one or display the major fault on the front panel of the backup processor if a 1775 S5 or SR5 is scanner number one switch to program load mode shut down the PLC 3 or PLC 3 10 system cause a fault message to appear on the screen of a programming terminal if one is being used If a fault occurs you can identify the nature of the fault and locate the source of the fault by observing indicators on the front panel of the processor observing indicators on each module examining bits in status words Diagnosing Faults with Processor Status Indicators The front panel of the processor has a 16 character display and several indicators Figure 6 1 Using these indicators you determine whether the processor is operating normally or if a major fault exists Table 6 A on page 6 3 and Table 6 B on page 6 4 describe how to interpret the status indicators on a processor when it is used as a primary or as a b
34. occur Both the primary and backup memory communication modules must be revision A C or later The backup to primary data transfer function must be selected in both the primary and backup processors via LIST function or message command The number of words to be transferred must be created beginning with S4 4 Note that there is no requirement to have the files the same length However the backup processor will send only the number of words contained in the smaller of the two backup and primary files This transfer occurs only in conjunction with a data table transfer or a file transfer from the primary to the backup 4 16 Using Message Instructions for Control Chapter 4 Using the 1775 MX Memory Communication Module Operation of a memory communication module using message MSG instructions follows the same convention as other modules in a PLC 3 system The memory communication module has additional functions however that let you enable and disable operation of memory communication modules from the ladder program Table 4 G lists the commands available for use in message instructions All of the functions available in LIST are also available in message instructions In addition there are four commands TRANSFER DATA TRANSFER lt file list gt DISABLE OUTPUTS PROGRAM CONTROL available in message instructions that are not available when using LIST control Table 4 G MSG Instruction Functions Command A
35. A A 011775 L3 A E 0 0 11775 S5 A G 1775 MX A C NTER NEXT gt MCM OPERATION CHASSIS 00 SLOT 06 SYSTEM ID 03 LIST CONTROL 1 2 3 4 5 6 7 8 9 1 1 F INACTIVE FILE TRANSFER DATA TABLE XFER EMORY DOWNLOAD LOCK SYSTEM UNLOCK SYSTEM ENABLE PROG COMP DISABLE PROG COMP E P ILE SELECTION ROG COMP LIMITS 0 1 BACKUP TO PRIMARY DATA TRANS THIS FEATURE CAN ONLY BE ENABLED DISABLED WHEN SYS TEM IS IN PROGRAM MODE THIS FEATURE MUST BE CONFI GURED IDENTICALLY IN BOTH THE PRIMARY AND BACKUP MX MODULES ENTER E TO ENABLE THIS FEATURE OR D TO DISABLE IT PROG COMP LIMITS O COMP DISABLI MAIN SUBROUTINE FAULT FILE SELECTIONS ED 1 00 00004 2 IO 00003 3 N23 00000 4 D2 5a L0 6 CO ENTER NEXT gt The MCM OPERATION menu shows you three things the source of control functions selections made in LIST 10980 I present operational status of the memory communication module Chassis and slot information appear directly beneath the title of the menu A system identification number which is derived from the chassis and slot numbers of scanner number one is also shown Chapter 4 Using the 1775 MX Memory Communication Module As shown in Table 4 B a heading which appears directly beneath the system identification i
36. ALLEN BRADLEY wy PLC 3 Programmable Controller Backup Systems User Manual Important User Information Because of the variety of uses for this product and because of the differences between solid state products and electromechanical products those responsible for applying and using this product must satisfy themselves as to the acceptability of each application and use of this product For more information refer to publication SGI 1 1 Safety Guidelines for the Application Installation and Maintenance of Solid State Control The illustrations charts and layout examples shown in this manual are intended solely to illustrate the text of this manual Because of the many variables and requirements associated with any particular installation Allen Bradley Company cannot assume responsibility or liability for actual use based upon illustrative uses and applications No patent liability is assumed by Allen Bradley Company with respect to use of information circuits equipment or software described in this text Reproduction of the contents of this manual in whole or in part without written permission of Allen Bradley Company is prohibited Throughout this manual we make notes to alert you to possible injury to people or damage to equipment under specific circumstances WARNING Tells readers where people may be hurt if procedures are not followed properly CAUTION Tells readers where machinery may be damaged or economic los
37. DATA function is equivalent to the DATA TABLE XFER function in LIST After the primary processor executes a message instruction containing the START DATA command the memory communication module continuously transfers the entire data table less the status section from the primary to the backup processor For the transfer to occur the primary processor must be in run mode or test mode however the backup processor may be in any mode Even if the backup processor is in program mode the data table will be transferred successfully If you switch the primary processor to program mode the transfer will stop and the memory communication module reverts to LIST control If you switch the processor to program mode then back to run mode or test mode the message instruction must be executed for the transfer to become active again The memory communication module forces the data table in the backup processor to be identical to the one in the primary processor Thus deletions as well as creations may take place in the backup processor Further if a section of the data table exists in the backup processor but not in the primary processor that section will be deleted in the backup processor there is sufficient memory available in the backup processor to accommodate the data table when the memory communication module 1775 MX executes a START DATA command If not enough memory is available the backup processor will shut down A CAUTION To guard
38. S MER F 15 13 Rungs Which Use Block Transfer Input Data To Control Block Transfer Outputs 5 7 Chapter 5 Programming Techniques Other Program Rungs 10982 1 5 8 Using Data Table Status Bits Chapter 5 Programming Techniques Another approach for reducing the amount of data transferred across a backup communication channel is to use Data Highway or Data Highway Plus communication Although you will still need a backup communication channel to provide protection against having both processors controlling outputs at the same time you can use a Data Highway or Data Highway Plus port as an additional backup communication channel For further information about using communication adapter modules refer to the 1775 KA Communication Adapter Module User s Manual publication 1775 6 5 1 and the 1775 S5 SR5 I O Scanner Communication Adapter Module User s Manual publication 1775 6 5 5 The data table status section of PLC 3 memory contains information about PLC 3 operation Table 5 A lists the status information for the backup system configuration Table 5 A Data Table Status Status Information File Word Bit Run Backup Bit S0 3 17 Backed up not backed up Bit S0 3 16 Communication Error Bit S0 2 10 Program Checksum S0 4 amp 5 1775 MX Module Communication S4 0 1775 MX Module Program Compare S4 182 1775 MX Module System ID S4 3 1775 MX Module Backup to Primary S4 4 19 Transfer Data Words Run Bac
39. a continuous file transfer It uses integer file 2 and the timer section of the data table 4 21 Chapter 4 Using the 1775 MX Memory Communication Module Figure 4 3 Example Rung Illustrating Continuous File Transfer B1 0 S0 3 IMSG Sete rete Reece ree A MESSAGE EN 00 E7 Control B0 0 Channel E2 14 1 DN ISTART N2 T ER Bit B1 0 00 is an internal storage bit used to control execution of the transfer command You can use any unused data table bit for this purpose Bit S0 3 17 is the run backup bit there is sufficient memory available in the backup processor to accommodate the files when the memory communication module 1775 MX executes a file transfer If not enough memory is available the backup processor will shut down A CAUTION To guard against damage to equipment make sure Important If the file list is modified while a file transfer is active the changes do not go into effect until the next time you invoke the START lt file list gt command 4 22 5 00 EN Chapter 4 Using the 1775 MX Memory Communication Module Transfer lt file list gt Command The TRANSFER lt file list gt command lets you transfer selected files from the primary processor to the backup processor one time You can select from 1 to 16 files for use with this function The TRANSFER lt file list gt command and START lt file
40. ackup processor respectively Chapter 6 Diagnosing Faults Figure 6 1 Processor Front Panel PROCESSOR aoa D c 5 OUTPUTS MEMORY PROTECT ON DPR A B C 0 oiea DATA 7jJL8jL9 t PERIPHERAL CHANGE D E F P FORCE CHANNEL 0 PROGRAM MEMORY L 4 5 6 J ADDR O E fH 1 8 jew ACCESS lon _ 2 3 gt LENA N T UST SHIFT Drel car Ay SA a 7 10921 Table 6 A Status Indicators for Primary Processor Indicator Status Description PROCESSOR GREEN Primary processor is active normal operation Major fault occurred OFF Power is off in the primary processor OUTPUTS GREEN Outputs enabled Outputs disabled or major fault OFF Not used PROGRAM GREEN Primary processor is in program load mode RED Major fault OFF Primary processor is not in program load mode ACCESS GREEN A peripheral device is connected to a peripheral communication channel and is on line channel active RED A peripheral device is editing the program or major fault OFF No peripheral communication channels are active 1 When automatic switchover is selected a major fault will turn all four status indicators red Chapter 6 Diagnosing Faults Table 6 B Status Indicators for Backup Processor Indicator Status Description PROCESSOR GREEN Backup processor is active normal operation in backup mode RED Major fault occurre
41. ackup is number of the backup scanner module Selected will be automatically modified before and after switchover This allows you to have identical configurations in both the primary and the backup processor Not Selected will remain the same both before and after switchover The primary and backup processors must have unique station numbers Regardless of which mode you select both the primary and the backup Data Highway and Data Highway Plus channels are active There is no selection for the backup Data Highway or Data Highway Plus channel to remain silent on the link until switchover 5 18 Chapter 5 Programming Techniques When you select backup you assign the same Data Highway or Data Highway Plus station number to both the scanner module in the primary processor and the one in the backup processor As long as the primary processor is controlling the outputs the station address of the Data Highway or Data Highway Plus channel in the backup processor is modified Table 5 E and Table 5 F show the station number modifications for Data Highway and Data Highway Plus respectively At switchover the Data Highway or Data Highway Plus station number in the backup processor assumes the station address assigned to it with the LIST function Table 5 E Data Highway Station Numbers for 1775 S5 SR5 Modules The backup scanner module assumes a If the station address between station address that is 000 and 276 100g higher t
42. backup processor you must change its Data Highway station number after performing a memory download during initial system configuration Lock Command The LOCK command lets you protect the ladder program in the current context from being edited by a programming terminal This protection remains in effect until you unlock the processor or place it in program mode The LOCK function is equivalent to the LOCK SYSTEM function in LIST When the primary processor executes a message instruction containing the LOCK command the memory communication module attempts to acquire the edit resource for both the primary and backup processors The edit resource is defined as the ability of a programming terminal to create and or edit the ladder program and manipulate the data table If a ladder program is already being edited with a programming terminal the memory communication module cannot acquire the edit resource until the editing session is terminated For the LOCK command to function properly the primary processor must be in run mode or test mode If you switch the primary processor to program mode the memory communication module unlocks both the primary and backup processors Even though a PLC 3 backup system is locked you can still create and delete PLC 3 memory sections edit contexts other than the current context Chapter 4 Using the 1775 MX Memory Communication Module You can check the status of each processor by looking at f
43. bbreviation Description STOP STO The memory communication module stops both continuous data transfers and continuous file transfers to the backup processor START lt file list gt STA lt file list gt The memory communication module transfers the selected files from the primary to the backup processor continuously You can select up to 16 files for the transfer TRANSFER lt file list gt T lt file list gt The memory communication module transfers the selected files from the primary to the backup processor one time only You can select up to 16 files for the transfer START DATA STAD The memory communication module transfers the entire data table except the data table status section from the primary to the backup processor continuously TRANSFER DATA D The memory communication module transfers the entire data table except the data table status section from the primary to the backup processor one time only DOWNLOAD The memory communication module stops any data transfer in progress and transfers the entire contents of PLC 3 memory from the primary to the backup processor LOCK LO The memory communication module acquires the edit resource for both the primary and backup processors This protects the ladder program in the current context from being edited with a programming terminal UNLOCK U The memory communication module releases the edit resource for both the primary and backup processors 4 17 Chapter 4
44. both the primary and backup processors via LIST or message command The number of words to be transferred must be created beginning with S4 4 Note that there is no requirement to have the files be the same length However the backup processor will send only the number of words contained in the smaller of the two files This transfer occurs only in conjunction with a data table transfer or a file transfer from the primary to the backup When enabling this feature data table transfers and file transfers must be stopped An ERROR 12 will result if any transfers are occurring Once the STATUS ON command has been initiated continuous data table and or file transfers may be re enabled If the command is sent to a memory communication module of an earlier revision an unknown command error ERROR 1 will result Status Off Command The STATUS OFF command lets you disable data transfer from the backup processor to the primary processor When the primary processor executes a message instruction containing the STATUS OFF command the memory communication module disables data transfer from the backup processor to the primary processor When disabling this feature data table transfers and file transfers must be stopped An ERROR 12 will result if any transfers are occurring Once the STATUS OFF command has been initiated continuous data table and or file transfers may be re enabled Chapter 4 Using the 1775 MX Memory Communication Module
45. cessor CAUTION To guard against damage to equipment be careful not to short any of the field wiring while removing terminal swing arms If shorts occur in field wiring equipment may be damaged Restarting The procedure for restarting a repaired processor depends on the backup a Repaired Processor system configuration and switchover method used To restart a repaired processor find the appropriate restarting method to use in Table 3 B then follow that procedure Table 3 B Restarting Procedure Selection Use This If You Have This Backup Configuration Restarting Procedure Page Scanner backup if using automatic switchover with no Method 1 3 6 switchback Scanner backup if using automatic switchover with Method 2 3 7 controllable switchback MX backup Scanner backup if using manual switchover Method 3 3 7 3 5 Chapter 3 Operating a Backup System Restart Procedure Method 1 1 Turn off both processors if they are not already off 2 Reconnect the backup cable to the number one scanner module in the repaired processor 3 Reconnect the terminal swing arms to all scanner modules in the repaired processor 4 Turn on the backup processor 5 Select program load mode in the backup processor 6 Verify that channel configurations values in data tables and user program are correct in the backup processor If there are any incorrect entries correct them before proceeding 7 Turn off the backup processor
46. ck transfer instruction s in both the primary and backup processors Then the ladder program in the backup processor should reinitialize the block transfer after switchover You should use memory communication modules or a backup communication channel to transfer block data transfers from the primary to backup processors For more information about system configuration refer to chapter 1 in this manual When you restart a repaired processor you must update its internal storage areas These are the areas that store dynamic variables for example the values of counters and timers To update the internal storage areas perform data transfers between the working and repaired processors using either memory communication modules or a backup communication channel 5 5 Chapter 5 Programming Techniques Reducing Backup Communication Overhead 5 6 A PLC 3 backup system using memory communication modules requires the least amount of communication overhead Data is transferred quickly and efficiently from the memory communication module in the primary processor to its partner in the backup processor over a dedicated parallel communication link In PLC 3 scanner backup systems the only practical method of getting data from the primary to the backup processor is by using a backup communication channel or Data Highway Data Highway Plus communication In some applications it may be possible to reduce the amount of data being transfer
47. ckup cable as shown See the instructions in Configuring 1775 MX Memory Communication Modules for information about installing the interconnect cables To configure scanner backup do the following 1 Locate the backup cable 2 Connect one end of the backup cable to the backup connector on the number one scanner module thumbwheel set to 1 in the primary processor 3 Connect the other end to the backup connector on the number one scanner module thumbwheel set to 1 in the backup processor 2 13 Chapter 2 Installing a Backup System Figure 2 12 Connections for Scanner Backup Primary Processor Backup Processor i TAT E Backup cable see text 10395 Application Cable Automatic switchover with no switchback 1775 CBA Automatic switchover with controllable switchback 1775 CBB Manual switchover 1775 CBB 2 14 Connecting the I O Channel Wiring Chapter 2 Installing a Backup System There are four I O serial communication channels per scanner Depending on your system architecture you can use one or more of them for I O communication Peer to peer communication Backup communication To do this you connect I O cables to the terminal swing arm and configure each channel for the type of communication desired You configure I O channels by using LIST Figure 2 13 shows how to identify the terminals on a terminal swing arm Figure 2 13
48. cur by making this substitution Figure 5 2 Example for False Seal in 10 2 00 3 t 2 299 A nnn nnn nnn 01 00 00 3 00 10981 1 If you use bit 03 0 as the seal in instead of the auxiliary contact 12 2 the backup processor would not set bit 03 0 at all unless it was transferred to the backup processor via a backup communication channel or memory communication module Even worse a similar problem could occur if the backup processor reads an input change that the primary processor misses or if the stop pushbutton is pressed for too short a time Forcing I O Executing Block Transfers Restarting a Repaired Processor Chapter 5 Programming Techniques The force table is not transferred from the primary to the backup processor over any communication channel Thus if forces have been set in the primary processor they will not be transferred to the backup processor If switchover occurs the backup processor will become active but no forces will be set To prevent this undesirable situation we suggest that you set the forces first in the primary processor and then in the backup processor When it is necessary to remove forces we suggest that you remove forces from the backup processor before removing them from the primary processor If switchover occurs while a block transfer is in progress the transfer may abort prematurely To ensure the integrity of block transfers you must enter the blo
49. d OFF Power is off in the backup processor OUTPUTS Not used RED Major fault OFF Backup mode PROGRAM Backup processor is in program load mode Major fault OFF Backup processor is not in program load mode ACCESS GREEN A peripheral device is connected to a peripheral communication channel and is on line channel active RED A peripheral device is editing the program or major fault OFF No peripheral communication channels are active 1 When automatic switchover is selected a major fault will turn all four status indicators red Diagnosing Faults with Module Status Indicators All PLC 3 modules have two self test indicators Table 6 C describes how to interpret these indicators Table 6 C Module Self Test Indicators Indicator amp Status pass O FAIL Description ON OFF Normal operation OFF ON Module fault ON ON Power up or system reset OFF OFF Processor shut off Most PLC 3 modules have one or more indicators to help you pinpoint the location of a fault See Figure 6 2 through Figure 6 4 Table 6 D through Table 6 F describe how to interpret the indicators on each module 6 4 Figure 6 2 Chapter 6 Diagnosing Faults Indicator Locations for 1775 S4 and 1775 SR Scanner Modules
50. dentifies the current source of control commands for the memory communication module Table 4 B Menu Headings This heading Tells you that LIST CONTROL operation of the memory communication module is being controlled by selections made in LIST PROGRAM CONTROL operation of the memory communication module is being controlled by message instructions in the ladder program BACKUP you are viewing LIST selections for the memory communication module in the backup processor These selections have no affect on system operation except for the Backup to Primary Data Transfer function as long as the primary processor is controlling outputs Important At switchover the backup processor takes control of the outputs and LIST selections in the backup processor take effect immediately As shown in Table 4 C symbols which appear to the left of the entries on the menu identify the LIST selections that have been made and the current operational status of the memory communication module Table 4 C Menu Symbols This symbol Means that the command has been selected in LIST and is active the command has been selected in LIST and would be active if module operation were under LIST control LIST selections could also be inactive if the primary processor is in program load mode the command has not been selected in LIST but is active This could occur for the following reasons operation of the module is being controlled by the
51. e switches for the various scanner modules To select the backup mode do the following 1 Set backup switches through 4 on the number one scanner module thumbwheel set to 1 in both primary and backup processors for the type of switchover desired See Table 2 A for 1775 S4A and 1775 SR scanners or Table 2 B for 1775 S5 and 1775 SR5 scanners Chapter 2 Installing a Backup System 2 Set all backup switches on all other scanner modules if any are present in both the primary and backup processors to the up position Figure 2 5 Location of Backup Switches for 1775 S4A and 1775 SR Scanner Modules F eny PPE 1234 i i c0 1_ l Lt 1 Top Edge of Module 18753 Figure 2 6 Setting Backup Switches on the 1775 S4A and 1775 SR Scanner Modules Not Used Not Used always UP always UP ON ON OFF Switch Positions UP Switch is away from board DOWN 1 2 3 4 ON Switch is toward board OFF OFF 4 4 Set per Set per Table 2 A Table 2 A 10794 1 Table 2 A Backup Switches on 1775 S4A and 1775 SR Scanner Modules Switchover Method Processor Automatic switchover with controllable switchback Automatic switchover with no switchback backup Manual switchover Stand alone mode Chapter 2 Installing a Backup System Figure 2 7 Location of Backup Switches for 1775 S5 and 1775 SR5 Scanner Modules Backup Switch at Bottom Edge of Module
52. e Netherlands FAX 414 382 4444 Tel 31 2975 60611 Telex 844 18042 FAX 31 2975 60222 Publication 1775 6 3 1 November 1991 Supersedes publication 1771 6 3 1 September 1985 As a subsidiary of Rockwell International one of the world s largest technology companies Allen Bradley meets today s challenges of industrial automation with over 85 years of practical plant floor experience More than 13 000 employees throughout the world design manufacture and apply a wide range of control and automation products and supporting services to help our customers continuously improve quality productivity and time to market These products and services not only control individual machines but integrate the manufacturing process while providing access to vital plant floor data that can be used to support decision making throughout the enterprise ASIA PACIFIC CANADA LATIN AMERICA HEADQUARTERS HEADQUARTERS HEADQUARTERS Allen Bradley Hong Kong Allen Bradley Canada Allen Bradley Limited Limited 1201 South Second Street Room 1006 Block B Sea 135 Dundas Street Milwaukee WI 53204 USA View Estate Cambridge Ontario NIR Tel 414 382 2000 28 Watson Road 5X1 Telex 43 11 016 Hong Kong Canada FAX 414 382 2400 Tel 852 887 4788 Tel 519 623 1810 Telex 780 64347 FAX 519 623 8930 FAX 852 510 9436 PN 955108 99 Copyright 1991 Allen Bradley Company Inc Printed in USA
53. e master number must be different from all slave numbers on the link The master number and all slave numbers must be unique and selected from numbers 81 through 89 As shown in the above procedure the twinaxial cable shield is always connected on 1775 S5 or 1775 SR5 scanner modules but alternately connected between 1775 S4A or 1775 SR scanner modules Chapter 2 Installing a Backup System Connecting an I O Channel for Backup Communication Any I O channel can be used for backup communication Figure 2 16 shows the connections when using I O channel 1 Figure 2 16 Connecting an I O Channel for Backup Communication Primary Processor Backup Processor o T o o M ii o Dl iE i j a E k ic i j p E i 5 a L p Ln ju My ai yO Bii U on D U i E an B EE o o IB 3 o o B E ka po aa e R cot e eg I lA cy fc iss jes Coy Cy iiss Ly S81 Gge bu Ly
54. e number one scanner in the repaired processor 2 Reconnect the terminal swing arms to all scanner modules in the repaired processor 3 Turn on the repaired processor 4 Check the configuration of each I O channel values in the data tables and the program in the repaired processor If there are any incorrect entries correct them before proceeding Manually reconfigure the repaired processor if necessary 5 Select run mode in the repaired processor Chapter Objectives Chapter Using the 1775 MX Memory Communication Module This chapter describes how to use 1775 MX memory communication modules Depending on your application you can program the memory communication module to transfer data from the primary processor to the backup processor to ensure that the data table in the backup processor matches that in the primary processor transfer data from the backup processor to the primary processor to provide data or status back to the primary download memory from the primary processor to the backup processor to initialize the backup processor with the same data and configuration as the primary processor control on line editing capability to prevent the primary processor or backup processor from being programmed independently compare the ladder programs in the primary and backup processors to ensure that all or part of the programs are identical voluntarily transfer control to the backup processor F
55. e that entire section of the ladder program Chapter 4 Using the 1775 MX Memory Communication Module To enter the program compare limits do the following 1 Select the command PROG COMP LIMITS from the MCM OPERATION menu by typing 10 ENTER 2 Enter the program limits into the PROG COMP LIMITS menu using the following syntax m s f where mis the limit for the main program section s is the limit for the subroutine program section f is the limit for the fault program section 3 To begin the program compare function select the command ENABLE PROG COMP from the MCM OPERATION menu by typing 7 ENTER Important Ifa limit is modified while a program comparison is in progress the new value will not be used until you select the command ENABLE PROG COMP again 4 15 Chapter 4 Using the 1775 MX Memory Communication Module Backup to Primary Data Transfer Command The BACKUP TO PRIMARY DATA TRANSFER command lets you enable the backup to primary data transfer function When enabling or disabling this feature the processor must be in program mode When you enable BACKUP TO PRIMARY DATA TRANSFER the backup processor transmits up to sixteen words from the memory communication module s data table status section beginning at S4 4 into corresponding data table locations of the memory communication module in the primary processor The following conditions must exist for the backup to primary data transfer to
56. el 1 terminals on the terminal swing arm of a scanner module in the backup processor For 1775 S4A SR scanner modules install a 1770 XT terminator to the I O channel terminals in the backup processor as shown in Figure 2 14 For 1775 S5 and SR5 scanner modules you can either install a 1770 XT terminal or select a terminator by using the internal switches as shown in Figure 2 17 Important If the internal terminator option is used the link will be unterminated if the swing arm is removed from the scanner 3 Connect the other end of the 1770 CD twinaxial cable to the I O channel 1 terminals on the terminal swing arm of the corresponding scanner module in the primary processor Connect one end of another 1770 CD twinaxial cable to the I O channel 1 terminals on the terminal swing arm of the scanner module in the primary processor Connect the other end of this cable to the designated I O device Repeat steps 1 through 5 for other channels used for I O communication Using LIST configure each channel for use as I O communication 2 17 Chapter 2 Installing a Backup System Connecting an I O Channel for Peer to Peer Communication Any I O channel can be used for peer to peer communication Figure 2 15 shows the connections when using I O channel 1 Figure 2 15 Connecting an I O Channel for Peer to Peer Communication Primary Processor Backup Processor IT pai Fee m o0 o0 o
57. fer occurs once each time you request it and it has a higher priority than the data transfer function After the primary processor executes a message instruction containing the DOWNLOAD command the memory communication module stops any active data transfer and immediately transfers the entire contents of the PLC 3 memory in the primary processor to the backup processor The transfer occurs once each time this function executes The backup processor cannot take control of outputs if the primary processor faults during a memory download The memory communication module resumes its previous operation at the conclusion of the transfer 4 25 Chapter 4 Using the 1775 MX Memory Communication Module 4 26 Important A memory download will not occur if the backup processor has insufficient memory to accommodate the memory contents of the primary processor Should this occur the memory communication module will abort the memory download function and resume operation an error occurs during download In this case the memory communication module aborts the memory download function and the backup processor shuts down the keyswitch on the primary processor is in the MEMORY PROTECT ON position This causes the primary processor to display an error message unless the ignore keyswitch option is enabled on privilege 72 Important If you are using a series A revision C or earlier communication adapter module 1775 KA in the
58. g When developing programs for a PLC 3 backup system equipped with memory communication modules certain instructions cannot be executed in the backup processor To program your PLC 3 backup system you can program around the disallowed instructions CAUTION To guard against damage to equipment do not attempt to execute any of the instructions listed below If you do the backup processor may shut down due to a fault bad address The following instructions are disallowed in a backup processor shift register BSL BSR file arithmetic ADF SBF MLF DVF NGF SQF file comparison SEQ SNE SLS SLE SGR SGE file logical ANF ORF XOF NTF file transfer MVF MMF first in first out FIFO register FFL FFU diagnostic DDT FBC communications MSG BTR BTW In a PLC 3 backup system the backup processor cannot execute some of the PLC 3 instructions When programming a PLC 3 backup system we suggest you insert the rung shown in Figure 5 8 into the ladder programs Chapter 5 Programming Techniques for the primary and backup processors Then place executable instructions above the rung and disallowed instructions below the rung Figure 5 8 Example for Disallowed Instructions 4 Allowed Instructions Disallowed Instructions 10987 1 Alternatives to the END instruction in this rung are to condition all disallowed instructions with an examine on of bit S0 3 17 or to use a JMP instruct
59. han the assigned station number 300g and 376g 100g lower than the assigned station number Important Never give the 1775 S5 SR5 module the reserved station address of 377g and when you select the backup operation you cannot give the module a station address of 277g Table 5 F Data Highway Plus Station Numbers for 1775 S5 SR5 Modules The backup scanner module assumes a If the station address between station address that is 00 and 378 40g higher than the assigned station number 40g and 77 40g lower than the assigned station number Chapter 5 Programming Techniques When you do not select backup you assign a unique Data Highway 000g to 376g or Data Highway Plus 00g to 77g station number to the scanner module in the primary processor and the one in the backup processor The backup will continue to operate with the same station number even after the switchover WARNING To guard against personal injury and damage to equipment do not assign the same station number to both scanner modules if you have not selected backup mode If both scanners are assigned the same number and backup is not selected two stations with the same station number will attempt to communicate on the link This may cause unpredictable machine motion Manual Switchover The following information applies if you selected Data Highway backup operation and configured your PLC 3 backup system for manual switchover Table 5 G lists the res
60. hannel PLC 8 Processor backup Memory Communication Cable cat no 1775 CM Memory Communication Cable cat no 1775 CM Ground Bus Plate 13 Connection between Power Supply System Common studs ANDO P WDM oo o oo 18720 2 4 Chapter 2 Installing a Backup System Figure 2 3 Connections for a PLC 3 10 Backup System Using Scanner Backup O O m aa D O 200 o nE N a Cu o E Sn G a ial ial sia U U 3 o eS cx Tt oa ess ER 5 iat O O Oo ii 8 To Earth 5 Ground 5 CUN J CRIE J O B O B 8 8 CI 8 fe 3 Had 3 8 3 8 S 8 3 8 a To other 4 A JU 4 AJU 1 0 Chassis in the Channel Blue ae Shield O 5 t s O i LO 1 PLC 3 10 Processor Primary 2 1771 I O Chassis cat no 1771 A1B A2B A3B A4B Clear O 3 Power Supply cat no 1771 P2 _ 4
61. iderations nananana aaa 2 6 Configuring the I O Chassis nanona aaaea 2 7 Configuring Scanner Modules nonna anaana 2 8 Connecting the I O Channel Wiring nannaa 2 1 Configuring 1775 MX Memory Communication Modules 2 2 Operating a Backup System 00eeeeeeees 3 1 Chapter Objectives 00 ccc eee e cee eee eens 3 1 Starting Up a Backup System nananana 3 1 Shutting Down a Backup System 0 00000 eee 3 4 Restarting a Backup System 00000 cece cease 3 4 Disconnecting a Faulted Processor 0 0000eae 3 5 Restarting a Repaired Processor 00eeeeeuee 35 Using the 1775 MX Memory Communication Module 4 1 Chapter Objectives n n ewe ch obyevew sees tobe eeees 41 Controlling the Operation of Memory Communication Modules 4 2 Using LIST Functions for Control 0 00 00 eee eens 43 Using Message Instructions for Control 5 4 17 Error Codes 0 2 ccc eee e cece eee eee ene eae eaeas 4 33 Table of Contents Programming Techniques 2 00eeeeeeees Chapter Objectives 0 0 cece eee eee eee Signal Conditioning 06 e cece eee eee eee Timers and Counters at Switchover 000005 Timing Considerations at Switchover 0000000 Forcing UO 282s steed euan etunesten tee area wees Executing Block Transfers 000 cence eee eees Resta
62. ile 4 word 0 of the status section For further information about interpreting status words refer to Using Data Table Status Bits in chapter 5 Important The PLC 3 backup system is not considered locked unless the edit resource is acquired for both processors When the PLC 3 backup system is locked a programming terminal cannot edit the ladder program in the current context Other programming devices must honor the edit resource Unlock Command The UNLOCK command lets you release the edit resource for both the primary and backup processors thus allowing you to edit the program in the current context with a programming terminal The UNLOCK function is equivalent to the UNLOCK SYSTEM function in LIST Enable Compare Command The ENABLE COMPARE command lets you compare specific sections of the ladder program in the backup processor with corresponding sections in the primary processor on a word by word basis When the primary processor executes a message instruction containing the ENABLE COMPARE command the memory communication module compares each section of the ladder program from the first rung through the specified rung If you set the limit for a particular section at zero that section will not be compared If the memory communication module cannot find the label comment number for a section it will compare that entire section of the ladder program See Table 4 J 4 27 Chapter 4 Using the 1775 MX Memory Communication Module
63. ion conditioned by an examine on of bit S0 3 17 to branch around groups of disallowed instructions If transferring the entire data table the instructions BSL BSR DDT and FBC must not be examined in the backup processor even if rung conditioned with the run backup bit You must either jump around these instructions or put them after the END statement For further information about programming see the PLC 3 Family Programmable Controller Programming Reference Manual publication 1775 6 4 1 Chapter Objectives How the Backup System Behaves When a Major Fault Occurs Diagnosing Faults This chapter describes how to diagnose faults in a PLC 3 backup system using status indicators on the front panels of processors and on the front panels of modules in the processors system status words Also it describes a simple diagnostic technique that can help you identify the program section and rung number of faults when they occur Before discussing fault diagnosis however you should review what happens when a processor encounters a major fault If the primary processor determines that a major fault exists while it is in run mode the primary processor will display the message DEACTIVE on the front panel of the primary processor if a 1775 S4A or SR is scanner number one or display the major fault on the front panel of the primary processor if a 1775 S5 or SR5 is scanner number one switch to program
64. itchover The first rung of the main routine as shown in Figure 6 5 initializes the data table status words and the E2 memory section words Bit S0 3 01 is used to condition the rung since this rung need only execute once after powering up in the RUN mode or after changing modes from PROGRAM to RUN Important This rung must be programmed before the conditional end rung which is often programmed in a backup system 6 9 Chapter 6 Diagnosing Faults Figure 6 5 Main Routine RM0 Rung j XOR to EXCLUSIVE OR Source A 9 0 0000000000000000 XOR EXCLUSIVE OR Source A S9 1 0000000000000000 Source B S9 1 0000000000000000 Source B 9 0 0000000000000000 Destin S9 0 0000000000000000 Destin S971 0000000000000000 MVS E MOVE STATUS Source MVS MOVE STATUS Source S 00000000000000 E2 2 1 0 2 1 00000000000000 S 9 0 0000000000000000 E22 022 0 0000000000000000 Destin Destin XOR EXCLUSIVE OR Source A S982 0000000000000000 Source B S9 2 0000000000000000 Destin Sor2 0000000000000000 9 0 00 00 10989 1 The first rung in the fault routine memory section is shown in Figure 6 6 This rung saves the contents of the failure status words by copying them into file 9 of the data table status area Figure 6 6 Fault Routine RF0 Rung 0000 MVS MOVE STATUS MOVE STATUS LBL
65. kup Bit The run backup bit file 0 word 3 bit 17 indicates whether or not the processor is acting as a backup processor This bit is set in the primary processor and reset in the backup processor Chapter 5 Programming Techniques 5 10 Backed up Not backed up Bit The backed up not backed up bit file 0 word 3 bit 16 is set when option switch 2 on the number one scanner module is in the down position The status of this bit is influenced by the switchover configuration The backed up not backed up bit is set in the primary processor when using the automatic switchover with no switchback configuration set in both the primary and backup processors when using the automatic switchover with controllable switchback configuration reset when using any other switchover configuration Communication Error Bit The communication error bit status file 0 word 2 bit 10 indicates the presence of a communication error This bit is set when either the primary or backup processor detects an error on a backup communication channel the primary processor detects an error on a peer to peer communication channel the designated input file is too small for the data received on either a peer to peer or backup communication channel Program Checksum The checksum provides a preliminary indication of whether or not the programs are exactly the same in the primary and backup processors When the checksums do not agree
66. kup processor automatically takes control of outputs when the primary Switchover with processor faults No Switchback No operator intervention required at switchover Shutting off the primary processor initiates switchover Both the primary and the backup processor must be shut down and restarted when re installing a repaired processor Not recommended for applications using multidrop modems with 1775 KA modules because the modem port is not disabled after a processor fault Automatic Backup processor automatically takes control of outputs when the primary Switchover with processor faults Controllable Switchback No operator intervention required at switchover Shutting off the primary processor initiates switchover Either processor can be the primary processor The backup processor does not have to be shut down when re installing a repaired primary processor Not recommended for applications using multidrop modems with 1775 KA modules because the modem port is not disabled after a processor fault Continued on Next Page 1 7 Chapter 1 Choosing a Backup Configuration 1 8 Switchover Method Manual Switchover Attributes When the primary processor faults the system shuts down as though no backup system were available Operator intervention is required at switchover Control of the process is lost until switchover occurs Quickly resume control of a process following a fault i
67. l cable to the I O channel 1 terminals on the terminal swing arm of the scanner module in the primary processor Connect the shield Connect the other end of this 1770 CD twinaxial cable to the designated peer to peer channel in another processor If this is a 1775 S4A or 1775 SR scanner module do not connect the shield Connect one end of another 1770 CD twinaxial cable to the I O channel 1 terminals on the terminal swing arm of this scanner module Connect the shield Connect the other end of this 1770 CD twinaxial cable to the designated peer to peer channel in another processor If this is a 1775 S4A or 1775 SR scanner module do not connect the shield Repeat steps 5 and 6 for up to 6 slaves and 1 master 2 19 Chapter 2 Installing a Backup System 2 20 8 Ifthe last scanner is a 1775 S4A or 1775 SR scanner module install a 1770 XT terminator to the I O channel 1 terminals as shown in Figure 2 15 For 1775 S5 and 1775 SR5 scanner modules you can either install a 1770 XT terminator or select a terminator by using the internal switches as shown in Figure 2 17 on page 2 23 9 Using the LIST function configure I O channel 1 in the backup processor for peer to peer communication Use the same peer to peer station number as the primary processor If the primary processor is a master configure the backup processor as a master If the primary processor is a slave configure the backup processor as a slave Important Th
68. l terminators removing the terminal swing arm from a module causes the communication channels to be unterminated For more information about terminators and I O channel wiring refer to the PLC 3 Programmable Controller Installation and Operation Manual publication 1775 6 7 1 2 23 Chapter 2 Installing a Backup System Configuring 1775 MX Memory To implement MX backup you need two 1775 MX memory Communication Modules communication modules one for the primary processor and another for the backup processor and one 1775 CM memory communication cable assembly The cable assembly consists of four cables Two of them are interconnect cables 3 feet long that eliminate the need for a 1775 CBA or 1775 CBB backup cable The other two cables are communication cables 30 feet long Figure 2 18 shows the connections required for MX backup Figure 2 18 Connections for MX Backup RCVG Primary Processor RCVG Backup Processor Interconnect Cable Memory Communication Cable Assembly cat no 1775 CM XMTG 12187 2 24 Chapter 2 Installing a Backup System To configure MX backup do the following 1 Insert one memory communication module in the primary processor and one in the backup processor A memory communication module can occupy any slot in a PLC 3 processor chassis however to obtain the best system performance in multi chassis systems you should place the mem
69. list gt command are quite similar The primary difference between them being that the TRANSFER lt file list gt command causes the transfer to occur only one time whereas the START lt file list gt command causes the transfer to occur continuously The syntax of both commands is identical See Figure 4 4 there is sufficient memory available in the backup processor to accommodate the files when the memory communication module 1775 MX executes a file transfer If not enough memory is A CAUTION To guard against damage to equipment make sure available the backup processor will shut down Important If you selected continuous file transfer previously you must stop it before you can use the TRANSFER lt file list gt command Use the STOP command to terminate a continuous file transfer Figure 4 4 Example Rung for Performing a One Time File Transfer S0 3 MSG RS a MESSAGE 17 Control B0 0 Channel E2 14 1 DN TRANSFER N3 ER Bit B1 0 00 is an internal storage bit used to control execution of the transfer command You can use any unused data table bit for this purpose Bit S0 3 17 is the run backup bit 4 23 Chapter 4 Using the 1775 MX Memory Communication Module 4 24 Start Data Command The START DATA command lets you transfer the entire contents of the data table except the status section from the primary processor to the backup processor The START
70. low the guidelines previously described for early communication adapter modules or select backup operation with the LIST function Important Do not select backup operation for multidrop modem applications because the modem port is not disabled after a processor fault If you select backup operation you must assign the same station address to both communication adapter modules Even though they have an identical station address the backup processor modifies its station number automatically before and after switchover To implement backup operation follow these steps 1 On both communication adapter modules set option switch 2 OFF This causes the Data Highway port on the communication adapter module in the primary processor to deactivate when automatic switchover occurs WARNING To guard against personal injury and damage to equipment make sure switch 2 is set correctly If not both communication adapter modules will assume the same station address at switchover causing a data highway communication shut down This may cause unpredictable machine motions 2 Use the LIST function to disable the modem and the Data Highway ports This allows you to change the LIST options of the communication adapters 3 Use the LIST function to select backup operation for the communication adapter modules in both the primary and backup processors 4 Use the LIST function to assign the same Data Highway station address to the communication adap
71. m control command to redirect control to the ladder program When the primary processor is repaired and restarted it becomes the backup processor and the memory communication module resumes operation Ifthe backup processor faults all data transfers in progress stop until the backup processor is repaired and restarted Once the backup processor is active again the memory communication module resumes operation You can view the status of a memory communication module by making a series of selections in the LIST menu You can view the status of a memory communication module from either the primary processor or the backup processor Figure 4 1 If you make selections from the backup processor however they have no effect on the operation of the memory communication module until the backup processor takes control of outputs The only exception is the backup to primary data transfer function it can be accessed through the backup processor Important In this manual the term MCM refers to the memory communication module not to the PLC 3 high speed interface and diagnostic software cat no 1775 MCM Chapter 4 Using the 1775 MX Memory Communication Module LIST Menu for Primary and Backup Processor Figure 4 1 SYSTEM MODE 1 TEST MONITOR 2 RUN MONITOR 3 PROGRAM LOAD 4 REMOTE ENABLE 5 SYSTEM STATUS 6 MODULE STATUS ENTER NEXT gt MODULES 011775 ME8
72. mming Manual publication 1775 6 4 1 for detailed information Stop Command The STOP command lets you discontinue continuous data table transfers continuous file transfers or both The STOP function is equivalent to the INACTIVE function in LIST After the primary processor executes a message instruction containing the STOP command the memory communication module stops transferring data tables files or both from the primary to the backup processor If you execute this command while a data or file transfer is active the current transfer will be allowed to complete before the stop function becomes effective Then all subsequent data table and file transfers will be inhibited 4 19 Chapter 4 Using the 1775 MX Memory Communication Module 4 20 Start lt file list gt Command The START lt file list gt command lets you transfer selected files from the primary to the backup processor You can select from 1 to 16 files for use with this function The START lt file list gt function is equivalent to the FILE TRANSFER function in LIST After the primary processor executes a message instruction containing the START lt file list gt command the memory communication module transfers the group of selected files from the primary to the backup processor continuously For file transfer to occur the primary processor must be in run mode or test mode If you switch the primary processor to program mode file transfer will stop
73. mmunication Module For example if the primary processor encountered a message instruction containing the command ENABLE COMPARE 1 2 0 assuming the proper label comment numbers exist in the sections of the ladder program the memory communication module would compare the section in the main routine of the ladder programs starting at the first rung and ending at the rung containing the label with comment number 1 compare the section in the subroutine of the ladder programs starting at the first rung and ending at the rung containing the label with comment number 2 does not compare the section in the fault routine of the ladder programs Important Some data appearing in the ladder diagram is actually contained in the data table If you alter a ladder diagram in either the primary or backup processor in such a way that the information in the data table changes but the information in the program section remains unchanged then the program comparison function will not detect a miscomparison This may happen when using the following instructions message send diagnostic detect block transfer timers file instructions counters bit shifts first in first out FIFO Disable Compare The DISABLE COMPARE command lets you disable the program comparison function The DISABLE COMPARE command is equivalent to the DISABLE PROG COMP in LIST When the primary processor executes a message instruction containing the
74. n 1 3 Chapter 1 Choosing a Backup Configuration Choosing a Backup There are two backup configurations Configuration scanner backup Figure 1 2 which uses only I O scanner modules MX backup Figure 1 3 which uses 1775 MX memory communication modules How Scanner Backup Works Figure 1 2 shows the implementation of scanner backup The number one scanner module controls switchover as well as backup peer to peer and T O communication channels Figure 1 2 Scanner Backup Configuration SCANNER MODULE 1 B U MODULE 1 B U 5 7 SCANNER BACKUP CABLE BACKUP COMMUNICATION PEER TO PEER l COMMUNICATION l vocommunication TO FROM OTHER PEER TO PEER CHANNELS CH2 O CH4 O TO FROM CH3 1 0 Mee ate a EAA OEA OE a ean A ee ee a es A 10972 1 The data table of the backup processor can be updated in three ways The backup processor listens only to discrete real world inputs The input output buffer transfers data files over the backup communication cable You must program move and move file instructions to transfer critical data table information Data Highway or Data Highway Plus communication 1 4 Chapter 1 Choosing a Backup Configuration How MX Backup Works Figure 1 3 shows the implementation of MX backup The scanner modules still control I O communication channels but the memory communication modules handle data tran
75. n LIST or the STATUS ON command from a message instruction up to 16 words are sent from the backup system to the primary system The backup system transmits a maximum of 16 words from the MX data table status area beginning at S4 4 into the corresponding data table status locations in the primary system The number of words to be transferred must be created beginning with S4 4 There is no requirement to have the files the same length However the backup system will send only the number of words contained in the smaller of the two backup and primary files You can use Data Highway or Data Highway Plus modules to connect the primary and backup PLC 3 processors to a data highway Two modules are required one in the primary processor and another one in the backup processor Series A Revision C or earlier 1775 KA Modules When using series A revision C or earlier communication adapter modules use the following guidelines assign a unique station address 000g to 376g to each communication adapter module if the programs in the primary and backup processors are identical then you must make sure all information sent to the primary processor is also sent to the backup processor examine the run backup bit on every rung used to transmit data Chapter 5 Programming Techniques Series A Revision D or later 1775 KA Modules When using series A revision D or later communication adapter modules you can either fol
76. n for the Memory Communication Module Status File 4 Word 1 in the Data Table a e RE e e Unused value always 0 E D Ladder program section 1 for main program 2 for subroutine 3 for fault routine User program section of PLC 3 memory always 4 oo context number Status File 4 Word 2 in the Data Table 17 16 15 14 19 12 11 10 7 06 05 os os 02 ot 00 This word stores the rung number where the memory communication module detected the miscomparison 10985 1 Word 2 gives you the rung number where the miscomparison occurred For example if word 2 contained the value 12 then the miscomparison is located on rung 12 of the ladder logic program section designated in status file 4 word 0 1775 MX Module System ID A system ID is automatically assigned to each 1775 MX module and stored in S4 3 status file 4 word 3 The MCM OPERATION menu in LIST also displays this system ID This ID is dependent on the physical location chassis number and slot number of scanner 1 Status File 4 Word 1 in the Data Table es a I Ae a eat Number of chassis E E Number of chassis slot in which Scanner 1 in which Scanner 1 resides 0 thru 3 resides 1 thru 6 10986 1 5 15 Chapter 5 Programming Techniques Programming Considerations for Data Highway and Data Highway Plus 5 16 1775 MX Module Backup to Primary Transfer Data Words In response to the BACKUP TO PRIMARY DATA TRANSFER i
77. n the power supplies of the primary and backup processors Use 1 inch braid or 8 AWG wire Ifthe primary and backup processors are in separate enclosures connect the ground bus plates of the primary and backup processors together Use 1 inch braid or 8 AWG wire Connect the ground bus plate of either the primary or backup processor but not both to earth ground a Use star washers to assure a positive ground connection between metal surfaces and ground lugs For detailed information about grounding see Wiring and Grounding Guidelines publication 1770 4 1 Use shielded cable for I O channel wiring as specified in the PLC 3 Programmable Controller Installation and Operation Manual publication 1775 6 7 1 to minimize noise pickup Also use shielded cable for peer to peer communication channels backup communication channels and Data Highway Data Highway Plus channels We recommend using 1770 CD twinaxial cable Belden 9463 or equivalent Chapter 2 Installing a Backup System Configuring the I O Chassis You must configure all I O chassis for backup mode operation Each I O chassis has eight switches Two of the switches switches 2 and 8 are especially important because they affect the operation of a backup system See Figure 2 4 for the function and location of the I O chassis switches
78. n the primary processor Easy to transfer between primary and backup processor Manual switchovers do not guard against unexpected shutdowns as well as automatic switchovers do We suggest this method for applications using multidrop modems with 1775 KA modules Installing a Backup System Chapter Objectives This chapter describes how to install PLC 3 and PLC 3 10 backup systems Specifically it provides recommendations for power supplies grounding shielding configuring I O chassis configuring scanner modules connecting I O channel wiring configuring memory communication modules Installing the Hardware In general the recommendations and procedures for installing a PLC 3 or PLC 3 10 backup system closely resemble those of a stand alone processor To install a backup system do the following read the power supply grounding and shielding recommendations configure all I O chassis configure all scanner modules connect and configure I O channels configure 1775 MX memory communication modules necessary only if MX backup will be used This chapter describes each of these tasks For additional detailed information about installing PLC 3 and PLC 3 10 processors see the PLC 3 Programmable Controller Installation and Operation Manual publication 1775 6 7 1 CAUTION To guard against damage to equipment make sure A that all modules in the backup processor are the same series and
79. ng a PLC 3 or PLC 3 10 system for backup communication you can guard against shutdowns caused by processor faults Shutdowns can also be caused by power losses or faults in equipment other than the programmable controller For these cases you must take other measures to guard against shutdown Important Backup does not protect you from faults caused by programming errors or system timeouts because the error or timeout will also occur in the backup processor Backup Terminology Some terms you should be familiar with are Backup communication communication between the primary and the backup processors Backup communication channel transfers data from the primary to the backup processor transfers data table values from the backup to the primary processor and identifies the default processor if a cable breaks A backup communication channel is required for backup systems using the scanner backup configuration Backup mode a mode in which a processor performs a listen only function monitors inputs without controlling outputs while remaining ready to take control of the outputs Backup processor a programmable controller which performs a listen only function monitors inputs without controlling outputs It remains ready to take control of outputs should a fault occur in the primary processor Backup system includes the primary and backup processor When we use the term processor we are referring to a processor chassis m
80. odules 2 8 Setting Switch 2 The processor restart lockout switch switch 2 must be ON so the backup processor is capable of restarting the I O chassis at switchover if necessary If the system has more than one I O chassis switch 2 must be ON in each chassis For more detailed information about the processor restart lockout feature refer to the PLC 3 Programmable Controller Installation and Operations Manual publication 1775 6 7 1 Setting Switch 8 The chassis I O to backup processor switch switch 8 must be ON so the backup processor can receive inputs from the I O chassis The backup processor will not be able to receive inputs from the I O chassis if switch 8 is set incorrectly that switch 8 on a 1771 A1B I O chassis with starting module group 0 is set to ON If this switch is not ON the backup processor will not receive inputs from the I O chassis A CAUTION To guard against damage to equipment make sure You set up and install scanner modules whether you are configuring a system for scanner backup or MX backup The only difference is the cable used between the backup connectors on the various modules To configure a scanner module you must set backup switches select a backup cable connect the backup cable connect I O channel wiring Setting Backup Switches Each scanner module has four switches for selecting a switchover method or stand alone mode Figure 2 5 and Figure 2 7 show the location of thes
81. odules cables and the other components needed for operation Channel configuration a procedure using the LIST feature of the processor to assign a specific operation to one of the channels on an I O scanner module Hardware configuration the manner in which the backup processor is installed with the primary processor Chapter 1 Choosing a Backup Configuration Primary processor the processor that is controlling outputs When switchover to the backup processor occurs the backup processor becomes the primary processor since now it is controlling outputs Stand alone processor a programmable controller that is not configured for backup Switchover transfer of control from the primary processor to the backup processor Backup Communication Backup communication is communication between the primary and backup processors Without backup communication the backup processor receives only input and peer to peer data Since the primary and backup processors may have started at different times and are not synchronized the data table values may be different in each processor You can reduce these differences by transferring internal storage points via backup communication You can establish backup communication using one or more of the serial I O channels as a backup communication channel the parallel data communication of the 1775 MX memory communication module Data Highway or Data Highway Plus communicatio
82. of interest Table 6 G Diagnostic Status Words Status Word Definition E2 2 1 0 2 0 Decoding the two least significant bits yields the ladder logic memory section RM RS or RF E2 2 1 0 2 1 Rung number at which fault occurred 0 1 System Major fault word The following routine saves the state of these three system memory status words to help you identify and locate faults in a ladder program The routine itself is short occupying only two rungs of a ladder program Chapter 6 Diagnosing Faults Creating the Fault Routine The fault routine requires two rungs one rung as the first rung in the main ladder program memory section RMO and the other as the first rung in the fault routine ladder program memory section RFO These two rungs copy diagnostic status words to storage words in the data table status section for safe keeping until they can be analyzed The status area was chosen so that if an MX is being used to transfer the data table the saved data will not be overwritten File 9 was chosen since it currently is not reserved by any module If this file should become reserved in the future simply pick another unused data table status file Table 6 H shows the data table addresses used by the fault routine to store the diagnostic information Table 6 H Storage Words used by Fault Routine This Address Stores 9 0 Memory section number 9 1 Rung number where fault occurred 9 2 Major fault which caused sw
83. of the data table is created the ERR indicator remains on until you reset the communication error bit S4 0 07 If you have not created the status section the error indicator remains on until the problem causing the communication error is corrected then it goes off automatically Chapter 6 Diagnosing Faults A Logic Diagnostic Routine 6 8 Diagnosing Faults with Status Word Bits Another method of diagnosing faults is to examine the contents of status words in the system memory The state of individual bits groups of bits or both can help you pinpoint the source of faults For more information about status words see the chapter Programming Considerations in this manual Additionally you will find detailed information on status words in the publication PLC 3 Family Programmable Controller Programming Reference Manual publication 1775 6 4 1 When the PLC 3 detects a major fault it looks for label 0 in the fault routine memory section You can enter a label with label number 0 as the first instruction in the fault routine section and the processor will execute a fault routine when it detects a major fault You can determine the cause of system failure by programming a fault routine and saving the fault status at the time of failure The processor stores ladder logic fault status information in section E2 of the system memory and major fault status in the data table status area file 0 Table 6 G lists the three memory words
84. on Adapter Module User s Manual 1775 6 5 5 Additionally you can use our publication index publication SD499 as a guide to further information about products related to the PLC 3 and PLC 3 10 processors Consult your local Allen Bradley Company sales engineer or distributor for information regarding this publication or others P 3 Chapter Objectives Backup Concepts Choosing a Backup Configuration The information in this chapter can help you understand backup concepts evaluate different backup configurations choose a switchover method A backup system consists of two processors configured in such a way that the backup processor will take control of outputs if the primary processor faults Figure 1 1 shows the basic concept of a backup system Figure 1 1 Basic Backup System BACKUP PRIMARY COMMUNICATION BACKUP PROCESSOR PROCESSOR TO FROM I O 10971 1 A second processor which is identical to the first is connected to the main processor During normal operation the backup processor operates in a listen only mode If the primary processor encounters a major fault the backup processor takes control of the outputs This transfer of control also can occur due to a loss of power to the primary processor or a broken cable Chapter 1 Choosing a Backup Configuration Why Use a Backup System Backup is useful for applications in which an unexpected shutdown is costly or otherwise undesirable By configuri
85. on module is being controlled by the ladder program selections made in LIST will not affect the operation of the memory communication module until either the ladder program executes a message instruction containing a LIST CONTROL command or the primary processor is placed in program load mode Transfer Control Command The TRANSFER CONTROL command lets you force a switchover from the primary processor to the backup processor After the primary processor executes a message instruction containing the TRANSFER CONTROL command the following events occur switchover begins the primary processor shuts down the backup processor takes control of outputs 4 31 Chapter 4 Using the 1775 MX Memory Communication Module 4 32 Status On Command The STATUS ON command lets you enable data transfer from the backup processor to the primary processor When the primary processor executes a message instruction containing the STATUS ON command the backup processor transmits up to sixteen words from the data table status section beginning at S4 4 of the memory communication module into corresponding data table locations of the memory communication module in the primary processor The following conditions must exist for the backup to primary data transfer to occur Both the primary and backup memory communication modules must be revision A C or later The backup to primary data transfer function must be selected in
86. on of memory communication modules you enter commands into the ladder program using one or more message instructions Figure 4 2 shows the format of a typical message instruction Figure 4 2 Example MSG Instruction for a Memory Communication Module tMSG sa pasos SSS San aes MESSAGE EN Control B0 0 Channel E2 14 1 DN lt command gt ER E E 5555 5 Chapter 4 Using the 1775 MX Memory Communication Module See Table 4 H when creating a message instruction Table 4 H Message Instruction Components Enter the Which is Control section and starting word of the control file The control file is usually a binary file and binary files must start at word 0 Channel always the address E2 14 1 where E2 is the module status area of PLC 3 memory 14 is the section number of the memory communication module and 1 is the number of the memory communication module lt command gt one of the function commands for controlling memory communication module operation Important You may enter either the entire name or the abbreviated name as listed in Table 4 G In the remainder of this section we describe the operation of each command Some functions require one or more parameters following the command Parameters you have to enter we enclose in angle brackets lt gt If you need additional assistance with message instructions refer to the PLC 3 Programmable Controller Progra
87. onding I O OFF Set channel or the channel is inactive CHx ON The channel is functioning properly Configured for The input file is too small at the processor receiving data peer to peer FLASHING The slave or master does not exist Communication retry communication OFF The channel is inactive CHx ON The channel is functioning properly Configured for The input file is too small at the processor receiving data backup FLASHING The partner is not responding communication OFF The channel is inactive 6 6 Chapter 6 Diagnosing Faults Table 6 E Data Highway Data Highway Plus Status Indicators for 1775 S5 SR5 Scanner Modules Indicator Status Description XMTG ON transmitting a message ROG ON receiving a message RY ON ready to transmit a message CER ON programming or communication error detected oS ON Data Highway Data Highway Plus channel is disabled Important When the scanner is polling both the XMTG and RCVG LEDs turn on Table 6 F Status Indicators for 1775 MX Memory Communication Modules Indicator amp Status PRI Description ON Processor in primary mode OFF Processor in backup mode OFF Processor faulted ERR ON Communication error detected between two memory communication modules OFF Communication normal between two memory communication modules Whenever possible communication between memory communication modules will continue even though the ERR indicator is on If the MX status area
88. or example you could switch over to the backup processor when performing maintenance on the primary processor disable the backup processor from assuming control of the outputs after switchover For example when on line editing is occurring in the primary processor but the changes have not yet been sent to the backup processor 4 1 Chapter 4 Using the 1775 MX Memory Communication Module Controlling the Operation of Memory Communication Modules 4 2 As shown in Table 4 A you can control operation of memory communication modules by using LIST functions see page 4 3 message MSG instructions see page 4 16 Typically you use LIST functions during the development of your application This approach lets you select and deselect options manually In addition to providing additional selections you can use message instructions to automate memory communication module setup once you are sure of the application By inserting message instructions into the ladder program the memory communication module can be configured automatically when powering up in the run mode or whenever the system changes from program mode to run mode Table 4 A LIST Functions and MSG Instructions You can transfer the contents of the data table from the primary to the backup processor continuously transfer the contents of selected files from the primary to the backup processor continuously transfer the contents of the data
89. ord 0 in the Data Table te Fa 18 i 6 00 Transmissions occurring Backup in RUN mode Continuous single xfer Backup in TEST mode Data table file xfer Backup in PROGRAM mode Program compare enabled Backup faulted Program compare done Backup outputs enabled Program compare fail Backup locked LIST program control Primary locked Backup to primary data Communications error xfer enabled 10984 1 Important Bit 17 preconditions bits 15 and 16 1775 MX Module Program Compare If an error occurred while executing a program comparison function you can pinpoint the rung location by examining words 1 and 2 of status file 4 As shown in Figure 5 6 word 1 gives you the extended address of the miscomparison For example if word 1 contained the hexadecimal value 0412 then the miscomparison is located in the user program section current operating context 1 in a subroutine This information was obtained as follows the value 4 designates the user program section of PLC 3 memory the value 1 designates the current operating context the value 2 designates the subroutine program section 5 13 Chapter 5 Programming Techniques Important Upon completing the program compare function the memory communication module sets either bit 12 or 13 in status file 4 word 0 to show the condition of the transferred data You must reset these bits before checking the status of the next program compare function Table 5 B Status File 4
90. ory communication module in the same chassis as the memory modules 2 Connect the XMTG end of a 1775 CM cable to the XMTG connector on the memory communication module in the backup processor 3 Connect the RCVG end of this cable to the RCVG connector on the memory communication module in the primary processor 4 Connect the RCVG end of the other 1775 CM cable to the RCVG connector on the memory communication module in the backup processor 5 Connect the XMTG end of this cable to the XMTG connector on the memory communication module in the primary processor 6 Connect one end of a 1775 CM interconnect cable to the backup connector on the number one scanner module in the primary processor 7 Connect the other end of this cable to the backup connector on the memory communication module in the primary processor 8 Connect one end of the other 1775 CM interconnect cable to the backup connector on the number one scanner module in the backup processor 9 Connect the other end of this cable to the backup connector on the memory communication module in the backup processor 10 Set the option switches on the number one scanner modules in both the primary and backup processor for automatic switchover with controllable switchback See Table 2 A on page 2 9 or Table 2 B on page 2 10 1775 CM cables so the weight of the cable does not cause stress at the connectors If you don t support the cables the wires may break A CAUTION
91. p system for automatic switchover At switchover the data highway port is disabled on the communication adapter module in the primary processor the station addresses of the Data Highway and modem ports on the communication adapter module in the backup processor change to those selected in LIST Table 5 H lists the conditional responses that can occur with automatic switchover Table 5 H Automatic Switchover Responses Switchover occurs and Then the processor is waiting for a response the response is ignored 5 21 Chapter 5 Programming Techniques Programming Considerations for Memory Communication Modules 5 22 another station on the Data Highway is initiating a message possibly neither of the processors will respond to the message You must program the other station to respond to this condition the other station will receive no indication that switchover has occurred You can however program a message instruction to execute a message upon switchover Figure 5 7 or attempt to send commands to the backup processor If you can communicate with the backup processor you know that switchover has not occurred another station is communicating with the primary processor The programming considerations for PLC 3 backup systems using memory communication modules include ladder programming for a PLC 3 backup system using memory communication modules disallowed instructions Ladder Programmin
92. ponses that can occur with manual switchover Table 5 G Manual Switchover Responses Switchover occurs and Then the processor is waiting for a response the response is ignored another station on the Data Highway is initiating a message possibly neither processor will respond to the message You must program the other station to respond to this condition the other station will receive no indication that switchover has occurred You can however program a message instruction to execute a message upon switchover Figure 5 7 or attempt to send commands to the backup processor If you can communicate with the backup processor you know that switchover has not occurred another station is communicating with the primary processor Important Be sure to turn off the faulted processor before initiating the switchover to the backup processor 5 20 Chapter 5 Programming Techniques Figure 5 7 Sending a Message at Switchover B1 0 S0 3 WMG GH Se Sse SSH See eee e ee eneeee F MESSAGE EN 00 EF Control B200 1 Channel E2 5 1 DN H045 N4 17 B3 5 ER Bit B1 0 00 is an internal storage bit used to control execution of the transfer command You can use any unused data table bit for this purpose Bit S0 3 17 is the run backup bit Automatic Switchover The following information applies if you selected Data Highway and configured your PLC 3 backu
93. re enable the outputs by using the ENABLE OUTPUTS command Enable Outputs Command The ENABLE OUTPUTS command lets you re enable the backup processor to assume control of the outputs after switchover When the primary processor executes a message instruction containing the ENABLE OUTPUTS command the memory communication module enables the outputs in the backup processor Chapter 4 Using the 1775 MX Memory Communication Module List Control Command The LIST CONTROL command lets you redirect control of a memory communication module from the ladder program to LIST Only the primary processor can execute the LIST CONTROL command After the primary processor executes a message instruction containing the LIST CONTROL command operation of the memory communication module will be controlled by selections in LIST Any subsequent message instructions containing commands intended for a memory communication module will be ignored Program Control Command The PROGRAM CONTROL command lets you redirect control of the memory communication module from LIST to message instructions in the ladder program of the primary processor Only the primary processor can execute a PROGRAM CONTROL command After the primary processor executes a message instruction containing the PROGRAM CONTROL command operation of the memory communication module will be controlled by subsequent message instructions in the ladder program As long as the memory communicati
94. red across the backup communication channel This provides faster backup communication updates Figure 5 3 illustrates one technique that could eliminate the need to transfer block transfer inputs to the backup processor This program minimizes the number of unnecessary block transfers Block transfer write operations are performed only if the done bit of the associated block transfer read operation is enabled The run backup bit is used to keep the done bit off in the backup processor This technique can eliminate the need to use backup communication for block transfer inputs if the following conditions are true only block transfer outputs depend on the block transfer input conditions the block transfer outputs can withstand a one time update time at switchover of twice the normal update time plus 100 milliseconds all operations using the block transfer input data require only current values of the input data If your system does not meet these conditions use backup communication to transfer the block transfer input data to the backup processor Chapter 5 Programming Techniques Figure 5 3 Programming for Block Transfer Inputs Run BTR Backup Done 5073 B200 12 EBT Reo ashes hee ee e BLOCK TRANSFER READ EN 17 LS Rack 12 Group 7 DN Module 1 Control B200 12 ER Data file D110 0 Length 64 Pee eet See eee E BTR BTR Done Error B200 12 B200 12 canal Yo SS a
95. rting a Repaired Processor 00eeeeeeee Reducing Backup Communication Overhead Using Data Table Status Bits 0 0c cece eee Programming Considerations for Data Highway and Data Highway Plus 2 2 c 228 2ic0 0ke diay eek hk woes Programming Considerations for Memory Communication Modules Diagnosing Faults 0 0 eee eee eee eee Chapter Objectives lt 0 mci c ddw odes chdwsewisidwecdes babs How the Backup System Behaves When a Major Fault Occurs Locating a Fault 22 25 oy dw tide dedudtdawiwdidss a A Logic Diagnostic Routine nanan cece eee Manual Objectives Audience What This Manual Contains Preface Preface This manual shows you how to install configure and operate a backup system configured with PLC 3 or PLC 3 10 processors In this manual we describe backup system concepts procedures for installing backup systems procedures for operating backup systems programming techniques fault diagnosis Before you read this manual or attempt to use a backup system you should be familiar with the PLC 3 or PLC 3 10 programmable controller Also you may need to be familiar with one or more optional modules used in backup systems Table A describes the contents of each chapter in this manual Table A Manual Contents If you want to read about Refer to Chapter an overview of backup concepts description of 1 Choosing a Backup Configura
96. rung number Not all faults are the result of ladder diagram execution Certain faults such as watchdog timeout or backplane fault will not record anything in S9 0 or S9 1 Status word S9 2 saves the major fault as recorded by the processor when the system failed Figure 6 7 identifies the meaning of the different bits used to represent the possible major faults For further definition of the major fault word see the publication PLC 3 Family Programmable Controller Programming Reference Manual publication 1775 6 4 1 Stack fault Bad instruction Bad address Backup cable fault Deactive Figure 6 7 Major Fault Bits Oe a A a 0 fs 0 io ba Chapter 6 Diagnosing Faults Configuration fault Memory parity error Hardware fault Major I O fault Watchdog timeout Backplane fault Bus extender fault I O configuration fault 11049 1 Automating the Diagnostics If the PLC 3 system uses a 1775 GA peripheral communication module or a 1775 S4B scanner module you can program a procedure to display the major fault and the possible rung at which the fault occurred For example if you used the following procedure you would display results as shown in Table 6 J FAULT IF IF IF IF IF IF IF IF IF IF IF IF IF IF IF IF LP WO 0 r o O e N H DODANHDUOBPWNEF CO N S 9 0 A BAND S 9 2 C 00 C 01 C 02 C 03 C 04 C 05 C 06 C 07 C 010 G 01 1 C 014 C 015 C 017
97. s can occur if procedures are not followed properly Warnings and cautions identify a possible trouble spot tell what causes the trouble give the result of improper action tell the reader how to avoid trouble Important We recommend that you frequently backup your application programs on appropriate storage media to avoid possible data loss PLC is a registered trademark of Allen Bradley Company Table of Contents Preface cccxcneechas susie dae anaes aw ieee ee P 1 Manual Objectives 0 000 e eee eee eee eee P 1 AUIEN occ ane asra apka ranean aueiedses tau EE E P 1 What This Manual Contains 0 00 cece eee aes P 1 WARNINGS CAUTIONS and Important Information P 2 Terms and Conventions 00 000 cece a P 2 Related Publications 0 000 c ccs e eee eee eees P 3 Choosing a Backup Configuration 1 1 Chapter Objectives os lt 2sse0se e 050005 dees eevee 1 1 Backup Concepts n n nnana nannaa nananana 1 1 Choosing a Backup Configuration 0005 1 4 Choosing a Switchover Method 00s0eeeeeee 1 7 Installing a Backup System 2 0eeeeeeeee 2 1 Chapter Objectives 2 22 tak ida chan ebdweaclacddecdede 2 1 Installing the Hardware 1 2 0 0 0 0 cece eee eee aes 2 1 Power Supply Considerations 000 cece eeuee 2 6 Grounding Considerations 0 c cee cece 2 6 Shielding Cons
98. sed to a larger value than has actually elapsed Timers having a time base of 10 milliseconds may be off by as much as 150 milliseconds 100 milliseconds may be off by as much as 300 milliseconds 1 second may be off by as much as 1 5 seconds In a similar manner the possibility exists that the counter accumulator may increment twice at switchover Timing Considerations at Switchover Chapter 5 Programming Techniques When using PLC 3 processors in a backup system configuration program scans are not synchronized and although switchover is fast approximately 100 milliseconds it is not instantaneous Therefore it is possible that the primary and backup processors could read different input conditions during a particular scan If all input signals are present for at least the recommended length of time the primary and backup processors will see the same input condition If these conditions are not met however outputs may be assigned different states in the two processors This could cause a sudden change in operation at switchover Although using a backup communication channel can reduce the probability of such an event it is better to avoid this condition by adjusting the program accordingly The best course of action is to consider the various options and risks while designing the system writing the program or both To illustrate this point consider the rung shown in Figure 5 1 This rung represents a 3
99. sfers between the primary and backup processors Figure 1 3 MX Backup Configuration Fe pee eda eae a 3 i aes aaah ean 3 PRIMARY PROCESSOR SCANNER MODULE 1 B U SCANNER MODULE 1 B U TO FROM OTHER PEER TO PEER CHANNELS CH1 CHI PEER TO PEER COMMUNICATION O i ce 0 COMMUNICATION pe O COMMUNICATION CH4 O CH2 TO FROM 9 CH3 INTERCONNECT CABLE MEMORY COMMUNICATION MODULE MEMORY B U COMMUNICATION MODULE B U BACKUP COMMUNICATION 10973 1 1 5 Chapter 1 Choosing a Backup Configuration 1 6 Selecting Scanner or MX Backup Table 1 A and Table 1 B summarize the attributes of scanner backup and MX backup respectively Choose the backup configuration most suitable for your application Table 1 A Scanner Backup Attributes Advantages Disadvantages No additional cost every 1775 S4A SR S5 and SR5 has this feature built in Table 1 B MX Backup Attributes Advantages Data table in the backup processor is virtually identical to the one in the primary processor No external hardware is needed High speed data transfer from the primary to the backup processor 100k words per second for continuous or 10k words per second for one time transfers Ability to transfer program data from the primary processor to the backup processor E
100. sufficient memory available in the backup processor to accommodate the files when the memory communication module 1775 MX executes a file transfer If not enough memory is available the backup processor will shut down A CAUTION To guard against damage to equipment make sure 4 9 Chapter 4 Using the 1775 MX Memory Communication Module 4 10 Data Table Transfer Command The DATA TABLE XFER command lets you transfer all of the data table sections except the status section section 13 from the primary processor to the backup processor continuously The memory communication module transfers all undefined sections i e 14 15 and so on as well The primary processor must be in run mode or test mode for transfers to occur If you switch the primary processor to program mode data table transfer becomes inactive The memory communication module forces the data table in the backup processor to be identical to the one in the primary processor Thus deletions as well as creations may take place in the backup processor Further if a section of the data table exists in the backup processor but not in the primary processor that section will be deleted in the backup processor LIST commands INACTIVE FILE TRANSFER and DATA TABLE XFER are mutually exclusive i e only one may be used at a time there is sufficient memory available in the backup processor to accommodate the data when the memory communication module 1775 MX e
101. switches as shown in Figure 2 17 5 Using the LIST function configure I O channel 1 for backup communication in both the primary and backup processors Important Use numbers 81 through 89 for the resident and partner numbers CAUTION To guard against damage to equipment make sure A that you configure each channel in the backup system with the same resident and partner numbers when using multiple backup communication channels If you use a different resident or partner number on different channels of the same processor both processors may shut down if the backup cable breaks 2 22 Chapter 2 Installing a Backup System Terminators The first and last physical device of each I O channel requires a terminator Use discrete terminators cat no 1770 XT for 1775 S4A SR scanner modules The 1775 S5 SR5 scanner modules have internal terminators that can be enabled disabled with a switch See Figure 2 17 and Figure 2 7 Figure 2 17 Selecting Terminators on 1775 S5 SR5 Scanner Modules Switch Positions UP DOWN a When DOWN a terminator is connected on the corre sponding communication channel Switch is away from board ON Switch is toward board oer Connect a terminator when the scanner is physically the first or last device on a Data Highway Data High way Plus I O peer to peer or backup communica tions link otherwise set the switch to the UP position 10979 1 Important When using interna
102. t change its Data Highway station number after performing a memory download Lock System Command The LOCK SYSTEM command lets you protect the ladder program in the current context of both the primary and backup system from being edited by a programming terminal This protection remains in effect until you unlock the processor or place it in program mode For this command to function properly the primary processor must be in run mode or test mode If you switch the primary processor to program mode the memory communication module unlocks both the primary and backup processors 4 11 Chapter 4 Using the 1775 MX Memory Communication Module 4 12 When you select the LOCK SYSTEM command the memory communication module attempts to acquire the edit resource for both the primary and backup processors The edit resource is defined as the ability of a programming terminal to create and or edit the ladder program in the current context and manipulate the data table If a ladder program is already being edited with a programming terminal the memory communication module cannot acquire the edit resource until the editing session is terminated Even though a PLC 3 backup system is locked you can still create and delete PLC 3 memory sections edit contexts other than the current context Important When the PLC 3 backup system is locked a programming terminal cannot edit the ladder program in the current context Other intelligen
103. t devices must honor the edit resource Important The PLC 3 backup system is not considered locked unless the edit resource is acquired for both processors You can check the status of each processor by looking at file 4 word 0 of the status section For further information about interpreting status words refer to Using Data Table Status Bits in chapter 5 Unlock System Command The UNLOCK SYSTEM command lets you release the edit resource for both the primary and backup processors thus allowing you to edit the program in the current context with a programming terminal Chapter 4 Using the 1775 MX Memory Communication Module Enable Program Compare Command The ENABLE PROG COMP command lets you compare the ladder program in the backup processor with the one in the primary processor on a word by word basis This function works in conjunction with the program compare limits selections See Table 4 F Table 4 F Program Compare If the memory communication module Then completes the program compare without error bit 13 is set in file 4 word 0 of the status section You must reset this bit The memory communication module continues the comparison until a miscompare occurs encounters a miscompare LIST will show bit 12 is set in file 4 word 0 of the status section the address of the rung containing the miscomparison is put into file 4 words 1 and 2 and bit 14 is reset in file 4 word 0 L Enable Program Compare
104. table from the primary to the backup processor one time transfer the contents of selected files from the primary to the backup processor one time stop further continuous transfers once the transfer in progress completes download memory from the primary to the backup processor control on line editing capability for a programmable terminal compare the ladder program in the backup processor with the one in the primary processor ar a transfer control to the transfer control to the backup processor noo processor Yes Yes No No Yes Yes Yes Yes By Using LIST Function MSG Instruction Yes Yes Yes Yes Yes Yes Yes Yes inhibit the backup processor from taking control of outputs when the primary processor faults transfer backup processor data to the primary Yes Yes processor Using LIST Functions for Control Chapter 4 Using the 1775 MX Memory Communication Module The following sections describe how to control memory communication modules by using LIST functions and message instructions The LIST functions for memory communication modules follow the same convention as other modules in a PLC 3 system Important Concerning the operation of LIST functions note the following points Ifthe primary processor faults switchover occurs and the backup processor takes control of outputs The backup processor assumes that LIST is active unless it encounters a progra
105. ter modules in both the primary and backup processors Legitimate station addresses range from 000g to 276g and 300g to 376g Important Never give the 1775 KA module the reserved station address of 377g and when you select the backup operation you cannot give the module a station address of 277g 5 17 Chapter 5 Programming Techniques As long as the primary processor is controlling outputs the station address of the communication adapter module in the backup processor is modified as shown in Table 5 C Table 5 C Data Highway Station Numbers for 1775 KA Modules The backup module assumes If the station address is between a station address that is 000g and 2763 100g higher than the station address assigned to the communication adapter module in the primary processor 300g and 3763 200g lower than the station address assigned to the communication adapter module in the primary processor At switchover the communication adapter module in the backup processor assumes the station address assigned to it with the LIST function 5 Use the LIST function to enable the port used to connect the primary processor to the backup processor i e the Data Highway port or the modem port 1775 S5 SR5 Modules When configuring the Data Highway and Data Highway Plus channel through LIST you must make a backup selection See Table 5 D Table 5 D Data Highway Options The Data Highway and Data Highway Plus station If b
106. text from being edited while in the run or test mode UNLOCK SYSTEM The memory communication module releases the edit resource for both the primary and backup processors ENABLE PROG COMP The memory communication module compares the ladder diagram program in the backup processor with the one in the primary processor on a word by word basis DISABLE PROG COMP The memory communication module prevents the execution of the program compare function PROG COMP LIMITS Lets you select specific sections of the ladder program to be compared when ENABLE PROG COMP has been selected BACKUP TO PRIMARY Lets you transfer up to 16 words from the backup to the DATA TRANSFER primary processor The following sections describe each LIST command in detail 4 6 Chapter 4 Using the 1775 MX Memory Communication Module Inactive Command The INACTIVE command lets you discontinue continuous data table and file transfers As long as the selection INACTIVE is active the memory communication module inhibits data and file transfers between the primary processor and the backup processor If a data or file transfer was in progress when you selected the INACTIVE function it will become effective on completion of the transfer in progress Then all subsequent data and file transfers will be inhibited File Transfer Command The FILE TRANSFER command lets you transfer a group of selected files from the primary
107. the programs are definitely different Just because the checksums agree however does not guarantee that the programs are identical Because of this you should not use the checksum as the only verification that the programs are identical You may use it as an additional check for example after you load a program from tape A 16 bit checksum is generated for the application program if you created words 4 and 5 in file O of the data table status section You create these words by using the create command or by referencing them in an application program instruction Chapter 5 Programming Techniques The checksum is stored in file 0 word 5 and the checksum done bit is stored in file 0 word 4 bit 17 of the data table status section The done bit is set when the checksum operation is completed It remains set until reset manually or cleared automatically by the application program Figure 5 4 shows one use of the checksum In this example the status value is compared to a known good value which you previously stored in file 0 word 1 of the binary section If the values are not equal the program jumps to an unused label label 255 The PLC 3 processor then declares a major fault BAD ADDRESS and shuts down The checksum done bit S0 4 17 keeps the PLC 3 processor from performing the comparison before a checksum is calculated Figure 5 4 Checksum Operation S0 4 NEQ 255 s A lt gt B
108. tion scanner and memory backup configurations procedures for installing a backup system wiring 2 Installing a Backup System diagrams procedures for starting up shutting down restarting 3 Operating a Backup System disconnecting and restarting a repaired processor controlling memory communication modules using 4 Using the 1775 MX Memory LIST commands and message instructions Communication Module signal conditioning timing requirements forcing I O 5 Programming Techniques block transfers status words considerations when using communication adapter and memory communication modules what happens when a fault occurs locating faults by 6 Diagnosing Faults using indicators and status words P 1 Preface WARNINGS CAUTIONS and Important Information Terms and Conventions P 2 Information that is especially important to note is identified by three labels WARNING CAUTION Important WARNING tells you of circumstances or practices that can lead to personal injury as well as damage to equipment CAUTION tells you of circumstances or practices that can lead to damage of equipment Important provides you with information that is important for the successful application of the PLC 3 backup system Some terms used in this manual may be unfamiliar to you We list these terms with a brief definition of each Bit terminology the states of logic bits are defined as follows ON OFF Set
109. to the backup processor You can specify from 1 to 16 files by using the file selection function When the selection FILE TRANSFER is active the memory communication module transfers the selected files from the primary to the backup processor continuously If the list of files contains a file that does not exist in the primary processor the memory communication module displays the message FILE LIST ERROR on the PLC 3 front panel or on the programming terminal proceeds to the next legitimate file in the list For the file transfer function to work properly the primary processor must be in run mode or test mode File transfer will stop if you switch the primary processor to program mode When you switch the primary processor out of program mode file transfer will become active again as long as the selection FILE TRANSFER is still active in LIST 4 7 Chapter 4 Using the 1775 MX Memory Communication Module File Selection Command To specify a group of files select the entry FILE SELECTION in the MCM OPERATION menu The files currently in the list are displayed followed by the prompt FILE SELECTION ENTER NEXT gt You select up to 16 files one at a time by entering information using the following syntax e sf ENTER where e is the entry number 1 to 16 s is the data table section specifier Table 4 E f is the file number Table 4 E Data Table Section Specifiers
110. up with Automatic Switchover with No Switchback Cat No 1775 CBA PRIMARY BACKUP PROCESSOR PROCESSOR SCANNER 1 SCANNER 1 BACKUP BACKUP CONNECTOR CONNECTOR 1775 CBA BACKUP CABLE SHIELD 10976 I 2 11 Chapter 2 Installing a Backup System Figure 2 10 Backup Cable Wiring for Scanner Backup with Automatic Switchover with Controllable Switchback Cat No 1775 CBB PRIMARY BACKUP PROCESSOR PROCESSOR SCANNER 1 1775 CBB SCANNER 1 BACKUP BACKUP CABLE BACKUP CONNECTOR CONNECTOR SWITCH 10977 1 A CAUTION To guard against damage to equipment make sure that switch 2 closes within 8 milliseconds of switch 4 switch 3 closes within 8 milliseconds of switch 1 throw the switch to change the processor that is designated as the primary processor to the processor currently controlling outputs the new primary processor may fault A CAUTION _ If these conditions are not satisfied when you 2 12 Chapter 2 Installing a Backup System Figure 2 11 Backup Cable Wiring for Manual Switchover Cat No 1775 CBB PRIMARY BACKUP PROCESSOR PROCESSOR SCANNER 1 1775 CBB SCANNER 1 BACKUP BACKUP CABLE BACKUP CONNECTOR CONNECTOR O O SWITCH TO SYSTEM COMMON 10978 I Connecting the Backup Cable Figure 2 12 shows how to connect a backup cable for the scanner backup configuration Important If you are configuring the system for MX backup instead of scanner backup do not connect the ba
111. wire circuit used to activate or deactivate a motor starter Figure 5 1 Example Rung for Motor Starter 10 2 00 3 Lash Las ss 01 00 10 2 02 10981 I Pressing the start pushbutton energizes input I2 0 This energizes output 03 0 which supplies power to the motor starter When the motor starter receives power an auxiliary contact closes that energizes input 12 2 2 2 seals in output 03 0 that is it keeps output 03 0 energized until the stop pushbutton is pressed 5 3 Chapter 5 Programming Techniques 5 4 If the start pushbutton is pressed for too short a time the input change may be seen by the primary processor but not by the backup processor Should this occur bit 03 0 would be set in the backup processor one program scan later than in the primary processor because input 2 2 from the auxiliary contact would be set and energize output 03 0 WARNING To guard against personal injury and damage to equipment examine output bit 03 0 in series with the auxiliary contact 12 2 Figure 5 1 for the seal in when using a stand alone processor If you force output O3 0 on removing the force will not return the motor to its initial state Now suppose you used the output bit 03 0 as the seal in instead of the input from the auxiliary contact 12 2 as shown in Figure 5 2 At first glance this appears to have the same effect as the previous example but a closer look reveals that a problem could oc
112. xecutes a data table transfer If not enough memory is available the backup processor will shut down A CAUTION To guard against damage to equipment make sure Chapter 4 Using the 1775 MX Memory Communication Module Memory Download Command The MEMORY DOWNLOAD command lets you transfer the entire contents of the PLC 3 memory from the primary to the backup processor This transfer occurs once each time you request it and has a higher priority than the data transfer function The backup processor cannot take control of outputs if the primary processor faults during the download After the transfer is completed the LIST menu is redisplayed and the memory communication module resumes operation Important A memory download will not occur if the backup processor has insufficient memory to accommodate the memory contents of the primary processor Should this occur the memory communication module will abort the memory download and resume operation an error occurs during download In this case the memory communication module aborts the memory download and the backup processor shuts down the keyswitch on the primary processor is in the MEMORY PROTECT ON position This causes the primary processor to display an error message unless the ignore keyswitch option is enabled on privilege 72 Important If you are using a series A revision C or earlier communication adapter module 1775 KA in the backup processor you mus
113. xtra features are available such as memory download memory compare backup status etc Easily configurable through LIST Simple restart procedure Backup communication channel is necessary for transferring data table and the transfer is relatively slow 8 words per 14 milliseconds External switch box may be required Processor restart procedure is not flexible Disadvantages More costly than scanner backup Requires an extra slot in each processor chassis Increased time required for other operations such as program scan This increase is approximately 10 for file intensive programs and approximately 15 for I O intensive programs You must consider this increase when developing your program and configuring your system The only permissible switchover method is automatic switchover with controllable switchback Choosing a Switchover Method Chapter 1 Choosing a Backup Configuration The three methods of switching control of outputs from the primary to the backup processor are automatic switchover with no switchback automatic switchover with controllable switchback manual switchover You can use any one of these methods for scanner backup but you must use automatic switchover with controllable switchback for MX backup Table 1 C lists the attributes associated with each method Table 1 C Switchover Method Attributes Switchover Attributes Method Automatic Bac

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