Modbus protocol
Contents
1. Index Field name Example 0 Slave address 04h 1 Function 01h 2 Byte count 02h 3 Data flags 17 10 CDh 4 Data flags 27 20 1Bh 8 Error check CRC Lo C4h 9 Error check CRC Hi OBh The status of flags 17 10 is shown as the byte value CD hex or binary 1100 1101 Flag 17 is the MSB of this byte and flag 10 is the LSB Left to right the status of flags 17 10 is ON ON OFF OFF ON ON OFF ON DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 6 of 23 DEI MODBUS PROTOCOL multi line 2 2 2 Function 03 03hex read registers Reads the binary of registers in the slave Address area for readin of registers multi line 2 multi line 2 Address area Data to request Table Measuring values Measuring values table 0 499 Timers used Set point table 500 999 Timers minimum Set point table 1000 1499 Timers maximum Set point table 1500 1599 Values used Set point table 2000 2499 Values minimum Set point table 2500 2999 Values maximum Set point table 3000 3499 Output a Set point table 5000 5499 Output b Set point table 9000 9499 4189340240B The max number of data query is limited of the length of the actual table or max 100 Query The query message specifies the stating register and quantity of registers to be read Example of a request to read 0 1 from multi line 2 slave device 1 Index F2. 1 Mode 2 2 Mode 3 3 Mode 4 4 Mode 5 5 Mode 6 6 De load 7 Start sync reg 8 Alarm inhibit 9 Breaker pos on Same content as address 26 in the measurement table DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 16 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B 4 5 Parameter table Offset Ch no Content Unit Delay Output Output Enable add a b ress 0 i h 8 1 1010 U BB High step 1 90 10 y y y y 2 1020 U BB High step 2 90 10 y y y y 3 1030 U BB Low step 1 20 10 y y y y 4 1040 U BB Low step 2 20 10 y y y y 5 1050 f BB High step 1 90 10 y y y y 6 1060 f BB High step 2 20 10 y y y y 7 1070 f BB Low step 1 20 10 y y y y 8 1080 f BB Low step 2 20 10 y y y y 9 1090 Reverse power 20 10 y y y y 10 1100 Over current 1 20 10 y y y y 11 1110 Over current 2 20 10 y y y y 12 1160 Over load 1 20 10 y y y y 13 1170 Over load 2 20 10 y y y y 14 1220 Unbalance curr 90 10 y y y y 15 1230 Unbalance volt 20 10 y y y y 16 1240 var import 20 10 y y y y 17 1250 var export 20 10 y y y y 18 1260 df dt ROCOF Hz 10 s y y y y 19 1262 df dt ROCOF time Per n y y y 20 1270 Vector jump Deg 10 n y y y 21 1310 DG high volt 1 960 10 y y y y 22 1320 DG high volt 2 90 10 y y y y 23 1330 DG low volt 1 90 10 y y y y 24 1340 DG low volt 2 90 10 y y y y 25 1350 DG hig
3. Examples e Write nominal frequency 4016 60Hz ID 1 60Hz 600Hz 10 0258h Address 2000 80 2080d 0820h Tx 01h 10h 08h 20h 00h 01h 02h 02h 58h 28h 6Ah Rx 01h 10h 08h 20h 00h 01h 02h 63h e Read nominal frequency 4016 60Hz Tx 01h 03h 08h 20h 00h 01h 87h A8h Rx 01h 03h 02h 02h 58h B8h DEh Read 0258h 600d DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 21 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B 4 6 Digital input table Address Terminal Description 1500 27 Reserved for digital input PCB 1 4 1528 43 De load 1529 44 Man governor up 1530 45 Man governor down 1531 46 Man AVR up 1532 47 Man AVR down 1533 48 Mode 1 1534 49 Mode 2 1535 50 Mode 3 1536 51 Mode 4 1537 52 Mode 5 1538 53 Mode 6 1539 54 Breaker position off 1540 55 Breaker position on 1541 23 Alarm inhibit 1542 24 Alarm acknowledge 1543 25 Sync start 1544 26 Control via external communication 1545 27 Block loss of mains DEIF AVS e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 22 of 23 EI 4 7 Digital output table MODBUS PROTOCOL multi line 2 4189340240B Address Terminal Description 2000 2001 Not used 2002 126 127 AVR down 2003 128 129 AVR up 2004 2015 Not used 2016 57 58 Governor up 2017 59 60 Governor down 2018 Depends
4. Content Type 38 Reserved 39 Reserved 40 Seen Generator seeming power Measured in VA 41 PHli142 0 359 Generator phase angle Measured in deg 42 PHli243 0 359 Generator phase angle Measured in deg 43 DH 1 0 359 Generator phase angle Measured in deg 44 PHlaBL2 L4 0 359 Busbar phase angle Measured in deg 45 PHlpBL1 DGL1 0 359 Busbar generator phase angle Measured in deg 46 df dtss 11 df dt Hz 100 s AT UsuppPLY Supply voltage Measured in V 10 4 2 Control register table write only Address Content Description 0 Power regulator 0 100 of nominal power set point Activated in menu 4041 1 PF regulator 60 100 stated as PF value 100 The value 100 means PF 1 set point Activated in menu 4045 2 Control Bit O This bit must be 1 when writing the command word command If the bit is O the control command is don t care Bit 1 Mode 1 Bit 2 Mode 2 Bit 3 Mode 3 Bit 4 Mode 4 Bit 5 Mode 5 Bit 6 Mode 6 Bit 7 De load Bit 8 Start sync reg Bit 9 Alarm inhibit Bit 10 Alarm ack This bit is automatically reset in multi line 2 3 Freguency regu 50 50Hz 10 Based on nominal freguency lator set point Activated in menu 4042 4 Voltage regula 100 100 10 of nominal voltage tor set point Activated in menu 4043 5 Reactive power 100 100 of nominal power A negative value means capaci regulator set tive reactive power and a positive value means inductive reactive point power Activate
5. address function code starting address and quantity of flags forced Here is an example of a response to the query shown above Index Field name Example 0 Slave address 01h 1 Function OFh 2 Flag address Hi 01h 3 Flag address Lo 00h 4 Number of flags Hi 00h 5 Number of flags Lo OFh 6 Error check CRC Lo 14h 7 Error check CRC Hi 33h DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 9 of 23 DEI MODBUS PROTOCOL multi line 2 2 4 Function 16 10hex write register Writes values into a sequence of registers Address area for writing of registers 4189340240B multi line 2 multi line 2 Address area Data to request Table Control Control table 0 499 Timers used Set point table 500 999 Values used Set point table 2000 2499 The max number of data query is limited of the length of the actual table and max 100 Example of a request to preset two registers starting at timer no to 00 60 and 00 70 hex in slave multi line 2 device 1 Index Field name Example 0 Slave address 01h 1 Function 10h 2 Starting address Hi 01h 3 Starting address Lo 28h 4 Number of registers Hi 00h 5 Number of registers Lo 02h 6 Byte count 04h 7 Data Hi 00h 8 Data Lo 60h 9 Data Hi 00h 10 Data Lo 70h 11 Error check CRC Lo FCh 12 Error check CRC Hi FBh Response The norma
6. network bus continuously including during the silent intervals When the first field the address field is received each device decodes it to find out if it is the addressed device Following the last transmitted character a similar interval of at least 3 5 character times marks the end of the message A new message can begin after this interval The entire message frame must be transmitted as a continuous stream If a silent interval of more than 1 5 character times occurs before completion of the frame the receiving device flushes the incomplete message and assumes that the next byte will be the address field of a new message Similarly if a new message begins earlier than 3 5 character times following a previous message the receiving device will consider it a continuation of the previous message This will set an error as the value in the final CRC field will not be valid for the combined messages A typical message frame is shown below Start Address Function Data CRC check End T1 T2 T3 T4 8 bits 8 bits N x 8 bits 16 bits T1 T2 T3 T4 How the address field is handled The address field of a message frame contains eight bits Valid slave device addresses are in the range of 1 247 decimal A master addresses a slave by placing the slave address in the address field of the message When the slave sends its response it places its own address in the address field of the response to let the master know
7. on type Start 2019 Depends on type Stop 2020 Not used 2021 Not used 2022 Not used 2023 Not used 2024 Not used 2025 5 6 Relay 1 2026 8 9 Relay 2 2027 11 12 Relay 3 2028 14 15 Relay 4 2029 17 18 Relay 5 on in short time DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Errors and changes excepted Page 23 of 23
8. 096 P f control mix factor None n n n n 60 2106 Volt control DB 10 n n n n 61 2107 Volt control gain None n n n n 62 2108 Volt control time ms n n n n 63 2116 var control DB 90 10 n n n n 64 2117 var control gain None n n n n 65 2118 var control time ms n n n n 66 2126 G U control mix factor None n n n n 67 2136 PF control DB None n n n n 68 2137 PF control gain None n n n n 69 2138 PF control time ms n n n n 70 Reserved 71 Reserved 72 Reserved 73 Reserved 74 Reserved DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 18 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B Offset Ch no Content Unit Delay Output Output Enable add a b ress 75 Reserved 76 Reserved 77 Reserved 78 Reserved 79 Reserved 80 3010 Start next 81 3020 Stop next 82 4016 Nom frequency Hz 10 n n n n 83 4017 Nom power kW n n n n 84 4018 Nom current A n n n n 85 4019 Nom voltage V n n n n 86 4026 Volt prim V n n n n 87 4027 Volt sec V n n n n 88 4028 Current prim A n n n n 89 4029 Current sec A n n n n 90 4031 Control settings P n n n n 91 4032 Control settings var n n n n 92 4033 Control settings PF None n n n n 93 4041 Comm bus control P nO n n n y 94 4042 Comm bus contr
9. 100 Generator cosinus phi Measured in cos phi 100 Negative value means capacitive cos phi N Peen Generator active power Measured in W Negative value means reverse power 13 Qcen Generator reactive power Measured in var Positive value means generated inductive reactive power 14 UsaLt42 Busbar Measured in V 15 Fes Busbar frequency L1 Measured in Hz 100 16 HI Exp Ucen Exponent generator voltage 16 LO Exp IGEN Exponent generator current 17 HI Exp P Qcen Exponent generator power reactive power 17 LO Exp Unn Exponent busbar voltage 18 HI 19 LO Ecen Energy counter Measured in kWh Max 300000MWh NOT YET IMPLEMENTED Version 1 42 20 Alarms Bit O 1010 U BB High step 1 Bit 1 1020 U BB High step 2 Bit 2 1030 U BB Low step 1 Bit 3 1040 U BB Low step 2 Bit 4 1050 f BB High step 1 Bit 5 1060 f BB High step 2 Bit 6 1070 f BB Low step 1 Bit 7 1080 f BB Low step 2 Bit 8 1090 Reverse power Bit 9 1100 High current step 1 Bit 10 1110 High current step 2 Bit 11 1120 High power step 1 Bit 12 1130 High power step 2 Bit 13 Unbalance current Bit 14 Unbalance voltage DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 13 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B Address Content Type
10. 21 Alarms Bit O O import Bit 1 Q export Bit 2 df dt Bit 3 Vector jump Bit 4 2030 Sync fail Bit 5 4220 Supply alarm Bit 6 Breaker close fail Bit 7 Breaker open fail Bit 8 Breaker position feedback fail Bit 9 Phase sequence error 22 Alarms Bit O 3010 U DG High step 1 Bit 1 3020 U DG High step 2 Bit 2 3030 U DG Low step 1 Bit 3 3040 U DG Low step 2 Bit 4 3050 f DG High step 1 Bit 5 3060 f DG High step 2 Bit 6 3070 f DG Low step 1 Bit 7 3080 f DG Low step 2 23 Reserved 24 Reserved 25 Reserved 26 Status Bit O Mode 1 Bit 1 Mode 2 Bit 2 Mode 3 Bit 3 Mode 4 Bit 4 Mode 5 Bit 5 Mode 6 Bit 6 De load Bit 7 Start sync reg Bit 8 Alarm inhibit Bit 9 Breaker position ON Bit 10 Reserved Bit 11 Reserved Bit 12 Reserved Bit 13 Reserved Bit 14 Reserved Bit 15 Reserved 27 Number of alarms 28 Number of unacknowledged alarms 29 Upe max Generator max voltage Measured in V 30 Upe min Generator min voltage Measured in V 31 Ussi213 Busbar voltage Measured in V 32 UnBL3 L1 Busbar voltage Measured in V 33 UBB max Busbar max voltage Measured in V 34 UBB min Busbar min voltage Measured in V 35 UBBL1 N Busbar voltage Measured in V 36 Uspsi2 n Busbar voltage Measured in V 37 Ussi3 n Busbar voltage Measured in V DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 14 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B Address
11. 83h 2 Exception code 02h 7 Error check CRC Lo COh 8 Error check CRC Hi F1h The master addresses a query to slave device 01h The function code 03 is for a Read Registers it reguests the status of the register at an address which is out of range 3 2 Exception codes Code Field name Meaning 01h Illegal function The function code rece ived in the query is not an allowable action for the slave 02h Illegal data address The data address rece ived in the guery is not an allowable address for the slave 03h Illegal data value A value contained in the query data fields is not an allowable value for the slave DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 12 of 23 EI 4 Data tables 4 1 Measurement table read only MODBUS PROTOCOL multi line 2 4189340240B Address Content Type Application version L1 L2 Generator voltage Measured in V L2 L3 Generator voltage Measured in V L3 L1 Generator voltage Measured in V L1 N Generator voltage Measured in V Generator voltage Measured in V Generator voltage Measured in V Generator frequency Measured in Hz 100 Generator current Measured in A Generator current Measured in A Generator current Measured in A ala O Oil OD A BR wW NM o alo Cos phi 99 0
12. EEN CER iR tas HYDD 5 2 2 Function 03 03hex read registers oo dort te cti rae er cbe deco des pde rie tu pde dat cs aeyn dung dela 7 2 3 Function 15 0Fhex write multiple Tags 8 2 4 Function To TOhex write Tedist6 amp li iie et Ren RR A Ge au nde De DOE e ONR CES Ru Deu sds 10 3 Exception pini veni eodeni ndo do ano nane n ob de ar nane anco ro an bv ea y Rd 11 3 1 Exception reception irme rene e et e e GWR eee reve ved e e EX e ER RNV FD y 11 3 2 Bxception COde uor cuido LE 12 4 Data E 13 4 1 Measurement table read only usada e Edu eoe sechs e De O De e pute De ethane 13 4 2 Control register table write only AANEREN 15 4 3 Command flags table write ONY 2 1 itecto ted vate et redde bn dU dete deb iacu deb abu NBT UAU epi devise HE 16 4 4 Status flags table read only ENNEN 16 4 5 Parameter table MERI ED 17 4 6 Digital input table ie ee ara ru suede tu addi vad oda eee ee de eee eee 22 Z r Engitaloutpul Ge iuit maw nats dotted exa doa eden tea deste o dene madden nas dnn Ting dort di Y dda Yd nd ead 23 DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 2 of 23 EI 1 1 1 2 1 3 DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com multi line 2 MODBUS PROTOCOL 4189340240B General information General introduction to multi line 2 Modbus Each message must be transmitted in a continuous stream Only the RTU mode can be used on multi line 2 communic
13. Modbus protocol ALL multi line 2 TYPES 4189340240B 9900000000006 PF 990ec0c00006og 59 60 St 62 63 64 65 66 G7 65 ap 707172 Service port larm Des Generator Paralleling Controller Alarm O Breaker on Power c O Regulator on multi 34 line PPU Self check ok O K Alarm inh amp G e RS 485 Modbus RTU DEIF A S Tel 45 9614 9614 Frisenborgvej 33 DK 7800 Skive Fax 45 9614 9615 Denmark E mail deif deif com DEI MODBUS PROTOCOL multi line 2 4189340240B CONTENTS 1 General INfOrmatiON eseu eeEEKAKKEEKRENNEREERERKECEKEEKKKREEREhAEEEK RKNKEEEKEKKEEEKEEKNKEEEKEKNEEEKEEANNENEEENEEENKNENEEREEEEAEEEKE A 1 1 General introduction to multi line 2 Modbus RHYL e eee eeeeccaeeeeeeeeeeeeeeecaaeeeeeeeeeteees 3 12 Transactions on multi line 2 Modbus Protocol Eiu seas ara ered FY TYDD nad 3 1 9 Thequery resporise cycle ee uu or ates itis oo Gee AG cans ee as Bs GG IG de ead GA TR ad 3 uan TI a ry E MEE 4 1 5 How the address field is handled RE 4 1 6 Contents ele Le DEE 4 1 7 How characters are transmitted sera 5 1 8 Error CHECKING a nee EE 5 2 PUD CHO S GY YG Vedi A RA FR RT WY A TA YY FWY WY TN YR YNN WY RW YR 5 2 1 Function 01 01hex read flag status cruce teint peo e ue pai HER ko Ruin
14. None n n n n 131 4543 f output max Hz 10 n n n n 132 4553 U output max V n n n n 133 4563 output max A n n n n 134 4504 P output min kW n n n n 135 4514 S output min kVA n n n n 136 4524 Q output min kvar n n n n 137 4534 PF output min None n n n n 138 4544 f output min Hz 10 n n n n 139 4554 U output min V n n n n 140 4564 output min A n n n n 141 Reserved 142 Reserved 143 Reserved 144 Reserved 145 Reserved 146 Reserved 147 Reserved 148 4976 Password None n n n n 149 Reserved DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 20 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B Refer to the user s manual of your multi line for information on e Availability of channels e Min max settings e Factory settings Note that several channels also depend on the options However it is possible to write to channels where the option is not set it is not possible to enable the channel E g if an attempt is made to write a 1 to the enable flag the 1 will be discarded and the enable flag remains O It is not possible to write to offset 0 These values are used for DEIF internal version control y means that the channel is writeable n means that a O can be written to the channel only n10 means that only the value 10 can be written
15. able Query The query message specifies the flag references to be forced The requested ON OFF status is specified by contents of the query data field A logical 1 in a bit position of the field requests the corresponding flag to be ON A logical requests it to be OFF The following page shows an example of a request to force a series of ten flags stating a flag in slave device 1 The query data contents are two bytes 01 04 hex 1001 0000 binary The binary bits correspond to the flags in the following way Bit01100000 10010000 Flag 15 14 13 1211 109876543210 The first byte transmitted 0 hex addresses flags 7 0 with the least significant bit addressing the lowest flag 0 in this set The next byte transmitted 01 hex addresses flags 14 and 8 with the least significant bit addressing the lowest flag 8 in the set Unused bits in the last data byte should be zero filled DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 8 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B Example for multi line 2 slave device 1 Index Field name Example 0 Slave address 01h 1 Function OFh 2 Flag address Hi 01h 3 Flag address Lo 00h 4 Number of flags Hi 00h 5 Number of flags Lo OFh 6 Byte count 02h 7 Force data 7 0 90h 8 Force data 14 8 60h 9 Error check CRC Lo C4h 10 Error check CRC Hi OBh Response The normal response returns the slave
16. ation Broadcast function is not implemented in multi line 2 and is therefore not allowed Error check field e Cyclical Redundancy Check CRC multi line 2 RS 485 hardware settings e 9600 or 19200 bps e 8 data bits e None parity e 1 stop bit Transactions on multi line 2 Modbus Protocol Standard Modbus ports on multi line 2 use an RS 485 compatible serial interface that defines connector pinouts cabling signal levels transmission baud rates Controllers communicate using a master slave technique in which only one device the master can initiate transactions called gueries The other devices the slaves respond by supplying the requested data to the master or by taking the action requested in the query The Modbus Protocol establishes the format for the master s query by placing into it the device address a function code defining the requested action any data to be sent and an error checking field The slave s response message is also constructed using Modbus Protocol It contains fields confirming the action taken any data to be returned and an error checking field If an error occurred on receipt of the message an exception response is generated in the slave The query response cycle Query Response Device address Device address Function Function Eight bit Eight bit data byte data byte Error check CRC Error check CRC The query The function code in the quer
17. d in menu 4044 If terminal 26 Control via external communication is activated the regulators are controlled via the Modbus The digital inputs Alarm ack and Alarm inhibit are always handled even if terminal 26 ON In menu 4040 it is selected if a set point is to be controlled by analogue input or by the control registers Mode 3 and or Mode 4 must be on It is possible to write to the control registers also when terminal 26 OFF The content of the control registers is not lost in case of supply failure so frequent updates are not necessary DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 15 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B Example how to control the freguency via the Modbus e Activate terminal 26 e Activate frequency control register in menu 4042 e Write the control command address 2 Bit 1 ON Bit 3 ON Bit 8 ON e Write in the control register address 3 the desired frequency offset 4 3 Command flags table write only Address Content Description 0 Mode 1 1 Mode 2 2 Mode 3 3 Mode 4 4 Mode 5 5 Mode 6 6 De load 7 Start sync reg 8 Alarm inhibit 9 Alarm ack This bit is automatically reset in multi line 2 Same function as address 2 in the control register table 4 4 Status flags table read only Address Content Description 0 Mode 1
18. h freg 1 90 10 y y y y 26 1360 DG high freg 2 90 10 y y y y 27 1370 DG low freq 1 90 10 y y y y 28 1380 DG low freq 2 90 10 y y y y 29 Reserved 30 Reserved 31 Reserved 32 Reserved 33 Reserved 34 Reserved 35 Reserved 36 Reserved DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 17 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B Offset Ch no Content Unit Delay Output Output Enable add a b ress 37 Reserved 38 Reserved 39 Reserved 40 2016 Sync df max Hz 10 n n n n 41 2017 Sync df min Hz 10 n n n n 42 2018 Sync DU max n n n n 43 2019 Sync t CB ms n n n n 44 2026 Blackout df max Hz 10 n n n n 45 2027 Blackout dU max n n n n 46 2028 Blackout enable nO n n n y 47 2036 General failure n1 y y y n 48 2055 Freq control droop 10 n n n n 49 2056 Freq control DB 10 n n n n 50 2057 Freq control gain None n n n n 51 2058 Freq control time ms n n n n 52 2066 Power control DB 20 10 n n n n 53 2067 Power control gain None n n n n 54 2068 Power control time ms n n n n 55 2076 Power ramp up speed 96 10 s n n n n 56 2077 Power ramp up point n n n n 57 2086 Power ramp down speed 10 s n n n n 58 2087 Power ramp down point n10 n n n 59 2
19. hod The CRC field checks the contents of the entire message The CRC field is two bytes containing a 16 bit binary value The CRC value is calculated by the transmitting device which appends the CRC to the message The receiving device recalculates a CRC during receipt of the message and compares the calculated value to the actual value it received in the CRC field If the two values are not equal an error results Only the eight bits of data in each character are used for generating the CRC Start and stop bits do not apply to the CRC When the CRC is appended to the message the low order byte is appended first followed by the high order byte The master is configured by the user to wait for a predetermined time out interval before aborting the transaction This interval is set to be long enough for any slave to respond normally If the slave detects a transmission error the message will not be acted upon The slave will not construct a response to the master Thus the time out will expire and allow the master s program to handle the error Note that a message addressed to a non existent slave device will also cause a time out Functions Function 01 01hex read flag status Reads the ON OFF status of discrete flags in the slave Address area for reading of status flags multi line 2 multi line 2 Address area Data to request Table Status Status table 0 499 Alarm active Set point table 500 999 Alarm ackn
20. ield name Example 0 Slave address 01h 1 Function 03h 2 Starting address Hi 00h 3 Starting address Lo 00h 4 Number of registers Hi 00h 5 Number of registers Lo 02h 6 Error check CRC Lo C4h 7 Error check CRC Hi OBh DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 7 of 23 DEI MODBUS PROTOCOL 2 3 multi line 2 4189340240B Response The register data in the response message are packed as two bytes per register with the binary contents right justified within each byte For each register the first byte contains the high order bits and the second contains the low order bits Example of a response to the guery Index Field name Example 0 Slave address 01h 1 Function 03h 2 Byte count 04h 3 Data Hi 00h 4 Data Lo 06h 5 Data Hi 00h 6 Data Lo 05h 7 Error check CRC Lo C4h 8 Error check CRC Hi OBh The contents of register O are shown as the two byte values of 00 06 hex The contents of register 1 are 00 05 hex Function 15 0Fhex write multiple flags Writes each flag 0 x reference in a sequence of flags to either ON or OFF Address area for writing of status flags multi line 2 multi line 2 Address area Data to request Table Commands Command table 0 499 Alarm acknowledge Set point table 1000 1499 Enable Set point table 3500 3999 The max number of data query is limited of the length of the actual t
21. l response returns the registers preset Slave address Function Example of a response to the query shown above code starting address and quantity of Index Field name Example 0 Slave address 01h 1 Function 10h 2 Starting address Hi 01h 3 Starting address Lo 28h 4 Number of registers Hi 00h 5 Number of registers Lo 02h 6 Error check CRC Lo COh 7 Error check CRC Hi 3Ch DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 10 of 23 DEI MODBUS PROTOCOL 3 1 multi line 2 4189340240B Exception Exception reception When a master device sends a query to a slave device it expects a normal response One of four possible events can occur from the master s query If the slave device receives the query without a communication error and can handle the query normally it returns a normal response If the slave does not receive the query due to a communication error no response is returned The master program will eventually process a time out condition for the query If the slave receives the query but detects a communication error CRC no response is returned The master program will eventually process a time out condition for the query If the slave receives the query without a communication error but cannot handle it for example if the request is to read a non existent register the slave will return an exception response informing the master
22. of the nature of the error The exception response message has two fields that differentiate it from a normal response Function code field In a normal response the slave echoes the function code of the original query in the function code field of the response All function codes have a most significant bit MSB of 0 This makes the function code value in an exception response exactly 80 hexadecimal higher than the value would be for a normal response With the function code s MSB set the master s application program can recognize the exception response and can examine the data field for the exception code Data field In a normal response the slave may return data or statistics in the data field any information that was requested in the query In an exception response the slave returns an exception code in the data field This defines the slave condition that caused the exception Example of a master query and slave exception response Query Index Field name Example 0 Slave address 01h 1 Function 03h 2 Starting address Hi 07h 3 Starting address Lo 03h 4 Number of registers Hi 00h 5 Number of registers Lo 02h 6 Error check CRC Lo COh 7 Error check CRC Hi 3Ch DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 11 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B Response Index Field name Example 0 Slave address 01h 1 Function
23. ol f nO n n n y 95 4043 Comm bus control U nO n n n y 96 4044 Comm bus control Q nO n n n y 97 4045 Comm bus control P nO n n n y 98 4051 Ext comm ID None n n n n 99 4052 19200 Baud nO n n n y 100 Reserved 101 4090 Ext comm error n1 y y y y 102 4110 Auto det run nO n n n y 103 Reserved 104 Reserved 105 Reserved 106 Reserved 107 Reserved 108 Reserved 109 Reserved 110 Reserved 111 Reserved 112 Reserved DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 19 of 23 EI MODBUS PROTOCOL multi line 2 4189340240B Offset Ch no Content Unit Delay Output Output Enable add a b ress 113 4220 Battery low V V 10 y y n 114 4231 German language nO n n y 115 Reserved 116 Reserved 117 Reserved 118 Reserved 119 Reserved 120 4502 P output type 0 or 4 n y n n 121 4512 S output type 0 or A n y n n 122 4522 Q output type 0 or 4 n y n n 123 4532 PF output type 0 or A n y n n 124 4542 f output type 0 or A n y n n 125 4552 U output type 0 or A n y n n 126 4562 output type 0 or 4 n y n n 127 4503 P output max kW n n n n 128 4513 S output max kVA n n n n 129 4523 Q output max var n n n n 130 4533 PF output max
24. owledge Set point table 1000 1499 Digital input Digital input table 1500 1599 Digital output Digital output table 2000 2499 Timer output Set point table 2500 2999 Timer running Set point table 3000 3499 Enable Set point table 3500 3999 The max number of data query is limited of the length of the actual table Page 5 of 23 DEI MODBUS PROTOCOL multi line 2 4189340240B The guery message specifies the stating flag and guantity of flags to be read Example of a guery to read 10 22 from multi line 2 slave device 4 Index Field name Example 0 Slave address 04h 1 Function 01h 2 Starting address Hi 00h 3 Starting address Lo OAh 4 Number of flags Hi 00h 5 Number of flags Lo ODh 6 Error check CRC Lo C4h 7 Error check CRC Hi OBh Response The flag status response message is packed as one flag per bit of the data field Status is indicated as 1 is the value ON and 0 is the value OFF The LSB of the first data byte contains the flag addressed in the query The other flags follow toward the high order end of this byte and from low order to high order in subsequent bytes If the returned flag quantity is not a multiple of eight the remaining bits in the final data byte will be padded with zeroes toward the high order end of the byte The byte count field specifies the quantity of complete bytes of data Example of a response to the query
25. which slave is responding Address 0 is used for the broadcast address Broadcasts are not allowed Contents of the error checking field The RTU mode error checking field contains a 16 bit value implemented as two eight bit bytes The error check value is the result of Cyclical Redundancy Check calculation performed on the message contents The CRC field is appended to the message as the last field in the message When this is done the low order byte of the field is appended first followed by the high order byte The CRC high order byte is the last byte to be sent in the message Additional information about error checking follows later in this chapter DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com Page 4 of 23 EI 1 7 1 8 2 1 DEIF A S e Tel 45 9614 9614 e Fax 45 9614 9615 e E mail deif deif com MODBUS PROTOCOL multi line 2 4189340240B How characters are transmitted serially When messages are transmitted on standard Modbus serial networks each character or byte is sent in this order left to right Least Significant Bit LSB Most Significant Bit MSB With RTU character framing the bit sequence is Without parity checking Start 1 2 3 4 5 6 7 8 Stop Note No even or odd parity checking is supported Error checking methods In RTU mode messages include an error checking field that is based on a Cyclical Redundancy Check CRC met
26. y tells the addressed slave device what kind of action to perform The data bytes contain any additional information that the slave will need to perform the function For example function code 03 will query the slave to read registers and respond with their contents The data field must contain the information telling the slave which register to start at and how many registers to read The error check field provides a method for the slave to validate the integrity of the message contents Page 3 of 23 DEI MODBUS PROTOCOL 1 4 1 5 1 6 multi line 2 4189340240B The response If the slave makes a normal response the function code in the response is an echo of the function code in the guery The data bytes contain the data collected by the slave such as register values or status If an error occurs the function code is modified to indicate that the response is an error response and the data bytes contain a code that describes the error The error check field allows the master to confirm that the message contents are valid RTU framing In RTU mode messages start with a silent interval of at least 3 5 character times This is most easily implemented as a multiple of character times at the baud rate that is being used on the network shown as T1 T2 T3 T4 in the table below The first field then transmitted is the device address The allowable characters transmitted for all fields are hexadecimal 0 9 A F Networked devices monitor the
Download Pdf Manuals
Related Search