ICD 19: Allen-Bradley PLC Communications
Contents
1. Applications which require this software should install it in their particular application environment The following installation instructions are for the EPICS UAE environment 3 0 1 ascii The UAE ascii directory contains the subdirectory cat_ascii to catenate new ASCII description files onto the base EPICS release The A B serial communications software contains no new records one new device and two new drivers e Change directory to ascii cat_ascii e Edit or create the file devSup ascii and add the following lines Allen Bradley DF1 ai INST_IO devAiAbDf1 AB DF1 serial NaO INST_IO devAoAbDf1 AB DF1 serial bar INST_IO devBiAbDf1 AB DF1 serial bo INST_IO devBoAbDf1 AB DF1 serial mbbi INST_IO devMbbiAbDf1 AB DF1 serial mbbo INST_IO devMbboAbDf1 AB DF1 serial e Edit or create the file drvSup ascii and add the following lines drvSerial drvAbDf1 ICD 19 Allen Bradley PLC Communications 1CD19 03 11 of 14 Problems with Serial Communications Software 3 0 2 src There are three source code files and two include files to add to the src directory devAbDfl c drvAbDf1 c drvAbDf1 h drvSerial c and drvSerial h e Change directory to src e Add the files devAbDf1 c drvAbDf1 c drvSerial c drvAbDf1 h and drvSerial h e Modify Makefile Vx and add the first three file names to the definition of SRCS c 3 0 3 startup Th2. July 1 1997 Added Ladder Logic example 2of 14 ICD19 03 ICD 19 Allen Bradley PLC Communications Layers in the Serial Communications Section Serial Communications The VME computer can communicate to the Allen Bradley PLC through an A B serial communications module located in an Allen Bradley rack This module the 1785 KE allows the VME computer to act as a node on the Data Highway Plus Figure 1 shows the physical connections FIGURE 1 2 0 Serial Communications between the VME computer and the A B PLC A B Rack VME Computer PLC 5 1785 KE MVME167 The following discussions follow the ISO OSI layering model for communications systems 6 In this model the layering is conceptual only and a protocol can be implemented within a layer or across layers The seven basic OSI layers are physical data link network transport session presentation and application Layers in the Serial Communications 2 1 The A B serial communications software uses a collapsed version of the ISO OSI model since the DF1 driver software implements the network transport and session layers Discussing EPICS device and record support within this model is somewhat problematical since EPICS does not follow the OSI model Physical Layer The three essential hardware elements needed for the PLC communications are the A B 1785 KE module the serial cable and a serial port on a VME crate running EPICS 1785 KE
3. 3 9 of 14 Layers int he Serial Communications 2 4 4 2 4 5 Binary Input Record The bi record reads one bit into the EPICS database from the underlying device support routines The value is enumerated into enabled or disabled states and for A B serial device support enabled means the bit value is low Binary Output Record The bo record writes one bit from the EPICS database into the underlying device support routines The value is enumerated into enabled or disabled states and for A B serial device support enabled means the bit value is low FIGURE 6 tyCo 1 41 23 rr SDIS bi23 2 4 6 2 4 7 a eee SLNK bi and bo record using A B serial device support nee ms _DOL FINK FINK SINK bo VAL bi VAL Npp yms SDIS LOUL ens bos tyCo 1 41 23 5 DTYP AB DF1 serial DTYP AB DF1 serial SCAN 1 O0 Intr Multi bit Binary Input Record The mbbi record reads a specified number of bits into the EPICS database from the underlying device support routines The input bit pattern is converted into an enumerated type in the VAL field using a lookup table of bit pattern to index conversion NOBT The number of bits field NOBT must be set to the size of the data read In the case of the A B serial device support this is a maximum of 16 bits Multi bit Binary Output Record The mbbo record writes a specified number of bits from the EPICS database into the unde
4. 4 Layers in the RIO Communications Section Il Remote I O Communications The VME computer can communicate to an A B PLC through a Remote I O RIO module located in an A B rack This module the 1771 DCM allows the VME computer to act as node on an RIO network usually with the 1771 DCM module as the only other node Figure 8 shows the physical layout of this communications system FIGURE 8 Remote I O communications between the VME computer and the A B PLC VME Computer A B Rack Remote I O Rack Bus VMEbus PLC 5 1771 DCM 6008 SV MVME167 5 0 Layers in the RIO Communications This section is TBD 6 0 Installation of the RIO Communications Software This section is TBD 7 0 Problems with the RIO Communications Software This section is TBD 14 of 14 1CD19 03 ICD 19 Allen Bradley PLC Communications
5. C cable Either an Allen Bradley cable 1770 CG can be purchased or one made according to the specifications of the 1785 KE manual 1 on page 4 5 Direct Connection to a Computer The cable should probably not exceed 50 feet although this distance varies according to application and baud rate For applications which require a modem either the Allen Bradley cable 1770 CP can be purchased or one made according to the 1785 KE manual 1 on page 4 8 Connection to a Modem Read the manual information about conforming modems before selecting equipment Data Link Layer Communications between the 1785 KE module and the VME serial port are through the RS 232 C protocol including full duplex and hardware handshaking The implementation of the data link layer in the 1785 KE is beyond the scope of this document The implementation of the RS 232 C communications in the VME crate is provided by two software drivers the specific serial port board driver and the EPICS serial driver drvSerial Serial Port Driver VxWorks Serial port board drivers are be provided by board vendors or may need to be written by the application developer Upon CPU initialization the driver installs in the 4 of 14 ICD19 03 ICD 19 Allen Bradley PLC Communications Layers in the Serial Communications VxWorks operating system and will either create device names for its ports or provide a mechanism for the application developer to do so The VxWor
6. CMD STS TNS TNS DLE ETX BCC 10 02 20 29 48 00 44 01 10 03 2A 6 The computer responds to the 1785 KE DLE ACK 10 06 2 3 3 Reading from the PLC This example reads the four words written above back from the PLC to the computer using the PLC 2 type command Unprotected Read FIGURE 3 PLC 2 Unprotected Read 1 The computer sends the command to the 1785 KE DLE STX DST SRC CMD STS TNS TNS ADR ADR SIZ DLE ETX BCC 10 02 29 20 01 00 45 01 28 00 08 10 03 40 6 of 14 1CD19 03 ICD 19 Allen Bradley PLC Communications Layers in the Serial Communications 2 The 1785 KE responds to the computer ACK 06 3 The 1785 KE sends the command to the PLC 5 1785 KE sends the command onto the DH and the PLC 5 node at 0x29 4 The PLC 5 sends the reply to the 1785 KE Gl PLC 5 executes the command formats a reply and sends it back to the 1785 KE 5 The 1785 KE sends the PLC 5 reply back to the computer DLE STX DST SRC CMD STS TNS TNS DATA DLE ETX BCC 10 02 20 29 48 O00 44 O1 22 11 44 33 66 55 88 77 10 03 2A 6 The computer responds to the 1785 KE DLE ACK 10 06 2 3 4 Ladder Logic Example The PLC program rungs see 7 in Figure 4 are not necessary to have communication working They have only been used for display purposes on the PLC end Communication will work with no PLC program as long as the PLC has a data fi
7. Created June 12 1997 Modified July 1 1997 Gemini Controls Group Report 1 0 ICD 19 Allen Bradley PLC Communications Bret Goodrich and Stan Karewicz ICD19 03 This Interface Control Document describes the EPICS communication to the Allen Bradley PLC via serial and Remote I O interfaces Introduction 1 1 1 2 1 3 Purpose This document describes the interfaces between the EPICS crate and the Allen Bradley PLC rack using either serial communications through a 1785 KE module or Remote I O through the 1771 DCM and 6008 SV modules Scope The audience for this document is EPICS programmers who need to communicate to an Allen Bradley PLC program This document describes the interface hardware the communications protocol and the EPICS programming It does not describe Allen Bradley ladder logic programming or Allen Bradley PLC hardware not used for the purpose of communication with the EPICS crate Documents The following documents are referenced in the text They should be read when further information is required on a topic 1 1785 KE Data Highway Plus Communications Interface Module Allen Bradley Publication 1785 6 5 2 May 1989 2 Direct Communications Module User s Manual Allen Bradley Publication 1771 6 5 27 October 1987 3 VMEbus Remote I O Scanner User Manual Allen Bradley Publication 6008 6 5 11 September 1995 ICD 19 Allen Bradley PLC Communications 1CD19 03 1 of 14
8. Introduction 4 5 6 7 EPICS Input Output Controller IOC Record Reference Manual Janet B Anderson and Martin R Kraimer Argonne National Laboratory December 1 1994 ICD 13 Standard Controller Bret Goodrich and Andrew Johnson ICD13 03 March 12 1997 The Open Book A Practical Perspective on Open Systems Interconnections Marshall Rose Prentice Hall 1989 PLC 5 Programming Software Release 5 0 Allen Bradley Publication 6200 6 4 7 December 1994 1 4 Abbreviations and Acronyms A B ai ao bi bo CRC DCM DH EPICS IOC ISO LANL mbbi mbbo OSI PLC RIO UAE Allen Bradley analog input record analog output record binary input record binary output record Cyclic Redundancy Check Direct Communications Module Data Highway Plus Experimental Physics and Industrial Control System Input Output Controller International Organization for Standardization Los Alamos National Laboratory multi bit binary input record multi bit binary output record Open Systems Interconnection Programmable Logic Controller Remote I O Universal Application Environment 1 5 Stylistic Conventions All software commands typed by the use are printed in a Courier Bold font All software responses returned from a computer are printed in a Courier font All references to the documents are by number i e 1 1 6 Revis ion History e June 12 1997 Creation e June 16 1997 Added ISO OSI model e
9. Module The 1785 KE module is a communications interface that links an intelligent RS 232 C asynchronous device to an Allen Bradley Data Highway Plus network The module has an external connector for the Data Highway Plus the RS 232 and a T50 Industrial Terminal Various modes of operation can be set by adjusting the four switch assemblies on the 1785 KE module Further description on these modes of operation along with examples of applications can be found in the 1785 KE manual 1 For communication with an EPICS crate the configuration of the 1785 KE module must be set to the following ICD 19 Allen Bradley PLC Communications 1CD19 03 3 of 14 Layers in the Serial Communications 2 2 2 2 1 e SWI full duplex CRC error checking no parity embedded responses e SW2 station number should be uniquely selected e SW3 DH 57 6 KBaud RS 232 9600 Baud local address e SW4 reserved VME Serial Port Any serial port on a VME computer may be used to communicate with the A B 1785 KE module as long as this port has implemented standard VxWorks device support Four serial ports are available on the Motorola MVME712 M transition module These ports are female DB 25 connectors with hardware selectable DTE DCE communications Serial Cable The RS 232 C serial cable connects the 1785 KE serial port with the EPICS crate The serial port on the 1785 KE is a female DB 15 connector requiring a modified RS 232
10. e object code file names for the above files must be added to the VxWorks startup script The definitions of three VxWorks variables must be added following the object code file names e Edit startup vws e Add the following lines in the record device driver etc section after the EPICS code has been loaded but before iocInit is executed ld lt version bin arch x o ld lt version bin arch drvSerial o ld lt version bin arch drvAbDfl o ld lt version bin arch devAbDfl o e Immediately following add the definitions for the VxWorks variables for the 1785 KE node address and the read and write block sizes The first variable must be the same as the address set on SW2 on the 1785 KE module Change the values in the example to your configuration drvAbDf1SrcStationNumber 11 drvAbDf1BlockReadDataSize 244 drvAbDf1BlockWriteDataSize 244 4 0 Problems with Serial Communications Software The known problems with the A B serial communications software are listed below Some are for informational purposes only 4 0 1 Reboot If the software has successfully linked with the 1785 KE module and is then rebooted it crashes after iocInit with an assertion failure A second reboot will succeed Then problem seems to be linked to the reception of a DF1 message before the software is ready to handle it 4 0 2 PLC 2 type unprotected writes The original source code has been modified by the Gemini Proj
11. e to the EPICS database from the underlying device support routines Because the A B serial device support reads words from the hardware some conversion method must be used LINR The linearization field LINR converts between the RVAL and VAL fields Conversion types may be No Conversion Linear or a user defined breakpoint table A conversion method of No Conversion will simply typecast the RVAL field into the VAL field A Linear conversion method requires values for ESLO and EGUL See the EPICS Record Reference Manual 4 for more information on ai record conversions 2 4 3 Analog Output Record The ao record writes a double precision value from the EPICS database to the underlying device support Because the A B serial device support writes words to the hardware some conversion method must be used LINR Conversion of the ao record s VAL field to the output RVAL value is similar to the ai record conversion described in Analog Input Record on page 9 Figure 5 shows an ai record reading word 23 from PLC node 41 on serial port tyCo 1 and an ao record writing to the same word FIGURE 5 ai and ao record using A B serial device support INP Npp wms DOL FLNK le ae FLNK SINK ao VAL Sea al VAL SDIS OUT tyCo 1 41 ae ws SDIS NPP NMS NPP oe ai23 a023 tyCo 1 41 23 DTYP AB DF1 serial DTYP AB DF1 serial SCAN 1I 0 Intr LINR NO CONVERSION ICD 19 Allen Bradley PLC Communications 1CD19 0
12. ect to use unprotected writes rather than protected writes The original source code communicated with 1771 KG and PLC 2 modules rather than with the 1785 KE and PLC 5 20 modules of the Gemini Project The PLC 5 does not accept protected write commands 4 0 3 PLC 2 type addresses The PLC 5 module accepts PLC 2 type addresses as long as the processor has a compatibility file with the same node number as the 1785 KE Only memory inside this 12 of 14 1CD19 03 ICD 19 Allen Bradley PLC Communications Problems with Serial Communications Software 4 0 data is accessible using the PLC 2 type addresses The software currently uses only the PLC 2 type 4 Error messages Error messages from the drivers have not been installed into the VxWorks error message symbol table The serial driver drvSerial uses error code 1000 and the drvAbDf1 uses error code 1001 although either of these can be changed in the include files if a conflict occurs e drvSerial error messages are define M_drvSerialLib 1000 lt lt 16 define S_drvSerial_OK 0 define S_drvSerial_noEntry M_drvSerialLib 1 no response on the queue define S_drvSerial_badParam M_drvSerialLib 2 unable to set option define S_drvSerial_paramConflict M_drvSerialLib 3 requested options conflict between applications define S_drvSerial_noInit M_drvSerialLib 4 init driver not called def
13. ine S_drvSerial_linkInUse M_drvSerialLib 5 serial device is in use define S_drvSerial_noParser M_drvSerialLib 6 no parser define S_drvSerial_EOF M_drvSerialLib 7 link down define S_drvSerial_OVF M_drvSerialLib 8 no msg term before buf ovf define S_drvSerial_queueFull M_drvSerialLib 9 queue quota exceeded define S_drvSerial_invalidArg M_drvSerialLib 10 invalid argument define S_drvSerial_noDevRead M_drvSerialLib 11 open for read failed define S_drvSerial_noDevWrite M_drvSerialLib 12 open for write failed define S_drvSerial_linkDown M_drvSerialLib 13 serial link is down define S_drvSerial_noMemory M_drvSerialLib 14 out of dynamic memory define S_drvSerial_noneAttached M_drvSerialLib 15 no app is using the link define S_drvSerial_internal M_drvSerialLib 16 internal e drvAbDf1 error messages are define M_drvAbDflLib 1001 lt lt 16U define S_drvAbDf1_OK 0 define S_drvAbDfl_badParam M_drvAbDflLib 1 bad parameter define S_drvAbDfl_noInit M_drvAbDf1lLib 2 init driver not called define S_drvAbDfl_linkDown M_drvAbDflLib 3 serial link is down define S_drvAbDfl_noMemory M_drvAbDflLib 4 out of dynamic memory define S_drvAbDfl_badFrame M_drvAbDflLib 5 corrupt input frame define S_drvAbDfl_abError M_drvAbDflLib 6 Allen Bradley error ICD 19 Allen Bradley PLC Communications 1CD19 03 13 of 1
14. interfaces the EPICS records with the network layer support provided by drvAbDf1 This layer is implement through EPICS device support for six standard records analog input ai analog output ao binary input bi binary output bo multi bit binary input mbbi and multi bit binary output mbbo 2 4 1 Common EPICS Record Fields The following fields are common to most or all the above records How they are used are also similar DTYP The Allen Bradley serial communications device support DTYP is AB DF1 serial SCAN The scanning mechanism SCAN for ai device support can use I O Intr along with Passive Event or any defined scan rate When processed using I O Intr the record will process on every change the drvAbDf1 driver detects in the value of the word or bit 8of 14 ICD19 03 ICD 19 Allen Bradley PLC Communications Layers in the Serial Communications INP or OUT The input INP or output OUT strings for the record identify the serial port destination node number and word number for the PLC word to be read or written An example string for ai ao mbbi or mbbo records would be tyCo 1 41 23 For bi or bo records the string also contains the bit number to read or write tyCo 1 41 235 Note the leading character identifying this string as a link type of INST_IO This string is fixed for each record instantiation 2 4 2 Analog Input Record The ai record returns a double precision valu
15. ks command iosDevShow will print a list of available devices some of these may be serial ports VxWorks provides serial port drivers for the Motorola MVME167 as part of the board support package The drivers are implemented on the CPU s four serial ports as ports tyCo 0 through tyCo 3 The console port uses tyCo 0 All examples in this document refer to the 1785 KE communications port as ty Co 1 2 2 2 EPICS drvSerial The EPICS serial port driver was implemented by Jeff Hill LANL for the Keck Observatory This driver interfaces a specified serial port to the EPICS control environment Because EPICS tasks are not allowed to block this driver hides the complexities of non blocking I O Input data is framed into individual messages and the driver can determine if the serial link is down to retransmit data at a later time The EPICS serial driver does not have a convenient or simple interface for user applications However for A B communications this complexity is hidden by another driver layer drvAbDf1 described in the following section To use the driver for A B communications it must be added to the local EPICS configuration compiled in an EPICS environment such as UAE then loaded onto the IOC at boot time 2 3 Network Layer The DF1 protocol provides the network transport and session layers of the OSI layers The protocol routes data between nodes network reliably transmits messages transport and establishes and maintains c
16. le corresponding to the 1785 KE DH node address and the size of this file matches or exceeds the size specified in the EPICS read and write buffers FIGURE 4 Ladder Logic Example Thu Jun 19 1997 Page 1 Program Listing Report PLC 5 20 File KEDEMO Rung 2 0 Rung 2 0 1785 KE DH address 13 octal 11 decimal this determines PLC file number accessed through serial port DH link PLC2 message format In this case VME system is writing into word N11 23 This rung is for display purposes only MOV instruction allows to observe bit patterns on the display of the output module located in Rack 0 slot 1 MOV MOVE Source N11 23 32 Destination 0 001 32 N11 23 MOV 2 0 2 1 0 001 MOV 2 0 ICD 19 Allen Bradley PLC Communications ICD19 03 7 of 14 Layers in the Serial Communications Rung 2 1 This rung can be used for verification of what is being written to PLC memory Value in word N11 23 is transferred into word N11 13 which can be in turn read back by VME via 1785 KE And again MOV to 0 04 is used for display purposes MOV SS gt oe MOVE Source N11 23 32 Destination N11 13 32 MOV MOVE Source N11 13 32 Destination 0 004 32 N11 13 MOV 2 1 2 1 N11 23 MOV 2 0 2 1 0 004 MOV 2 1 Rung 2 2 l END OF FILEJ 2 4 Presentation Layer The presentation layer of the PLC communications
17. onnections between the nodes session 2 3 1 EPICS drvAbDf1 The EPICS A B DF driver was implemented by Jeff Hill LANL for the Keck Observatory This driver transmits and receives ANSI F1 full duplex messages between the 1785 KE and VME computer The messages are formatted to be retransmitted by the 1785 KE module onto the Data Highway Plus and received by the requested PLC module The driver operates by reading a block of data from the PLC at a fixed rate of 8 Hz Data being read from the PLC to the EPICS database is then transferred to the appropriate record and I O INTR scanning is triggered if needed Data to be written to the PLC is then transmitted to the 1785 KE for retransmission The driver initialization must have the source node address of the 1785 KE and the size of the read and write memory buffers The source node address is used in all data messages to identify the DH initiator The read and write buffer sizes are used to perform block transfers of the PLC memory for performance reasons The sizes must be less than or equal to the memory size specified in the PLC module The command format used for the data transmission across the serial line uses the PLC 2 type commands These type of commands place some constraint upon the presentation of the PLC data to the VME computer Most importantly the PLC data to be transferred must be in one PLC file with the same file number as the 1785 KE ICD 19 Allen Bradley PLC Communicati
18. ons 1CD19 03 5 of 14 Layers in the Serial Communications module node address Thus if the 1785 KE node address is 0x20 the PLC program must have a compatibility file number 0x20 with the required data The use of PLC 3 type commands which the PLC 5 module supports would remove this restriction but has not been implemented in the EPICS A B DF1 driver The following examples of DF1 transactions have been lifted from the 1785 KE module manual 1 In these examples the computer or 1785 KE node address is 0x29 and the PLC 5 node address is node address 0x20 Note that these examples use BCC error checking while the EPICS driver uses CRC error checking 2 3 2 Writing to the PLC This example writes four words or eight bytes of data from the computer to the PLC 5 using the PLC 2 type command Unprotected Write FIGURE 2 PLC 2 Unprotected Write 1 The computer sends the command to the 1785 KE DLE STX DST SRC CMD STS TNS TNS ADR ADR DATA DLE ETX BCC 10 02 29 20 08 00 44 0T 28 00 22 11 44 33 66 55 88 77 10 03 DE 2 The 1785 KE responds to the computer DLE ACK 3 The 1785 KE sends the command to the PLC 5 The 1785 KE sends the command onto the DH and the PLC 5 node at 0x29 4 The PLC 5 sends the reply to the 1785 KE The PLC 5 executes the command formats a reply and sends it back to the 1785 KE 5 The 1785 KE sends the PLC 5 reply back to the computer DLE STX DST SRC
19. rlying device support routines The enumerated type VAL field is converted to an output bit pattern using a lookup table of index to bit pattern conversion NOBT The number of bits field NOBT must be set to the size of the data read In the case of the A B serial device support this is a maximum of 16 bits 10 of 14 ICD19 03 ICD 19 Allen Bradley PLC Communications Installation of Serial Communications Software FIGURE 7 mbbi and mbbo record using A B serial device support nee nus INP Nep yug DOL SL hos SS FINK SLNK OUT NPP nus SLNK mbbo NPP NMS mbbi 4S tyCo 1 41 23 0 wig SDIS VAL NPP Nas SDIS VAL tyco l 41 23 0 mbbi23 mbbo23 DTYP AB DF1 serial DTYP AB DF1 serial SCAN 1 0 Intr ZRVL 0 ZRST IDLE ZRSV NO_ALARM ZRVL 0 ZRST IDLE ZRSV NO_ALARM ONVL 1 ONST MOVING ONSV NO_ALARM ONVL 1 ONST MOVING ONSV NO_ALARM THVL 2 TWST STOPPING TWSV NO_ALARM TWVL 2 TWST STOPPING TWSV NO_ALARM THVL 4 THST STOPPED THSV NO_ALARM THVL 4 THST STOPPED THSV NO_ALARM FRVL 8 FRST ERROR FRSV MAJOR FRVL 8 FRST ERROR FRSV MAJOR NOBT 16 NOBT 16 2 5 Application Layer An EPICS database provides the application layer of the OSI model Such a database would be the Enclosure Control System communications with the A B rack controlling the carousel motion 3 0 Installation of Serial Communications Software The A B serial communications software is not part of the standard EPICS distribution nor of the Gemini EPICS distribution
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