Manual

ManualsBrandsDespatch ManualsControl panelProtocol Plus Modbus Communications

Chromalox Instruments and Controls

A-51643 Rev. 6 10/06/03 iii

5.1 FUNCTION SET OVERVIEW .......................................................................................................................... 20

5.2 REGISTER AND I/O FUNCTION SET DESCRIPTION FOR PROTOCOL

PLUS .................................................. 21

5.2.1 [01] Read Outputs ................................................................................................................................. 21

5.2.2 [02] Read Input Discretes ...................................................................................................................... 22

5.2.3 [03] Read Holding Registers (Read Multiple Registers) ....................................................................... 23

5.2.4 [04] Read Input Registers ...................................................................................................................... 24

5.2.5 [06] Write Single Register ..................................................................................................................... 25

5.2.6 [16] Write Multiple Registers ................................................................................................................ 26

5.3 DIAGNOSTICS AND SUPPORT DESCRIPTION FOR PROTOCOL

PLUS ........................................................... 28

5.3.1 [08] Diagnostics .................................................................................................................................... 28

5.3.1.1 [08 00] Return Query Data ............................................................................................................................ 28

5.3.1.2 [08 01] Restart Communications Option ....................................................................................................... 29

5.3.1.3 [08 02] Return Diagnostic Register ............................................................................................................... 29

5.3.1.4 [08 04] Force Listen Mode Only ................................................................................................................... 30

5.3.1.5 [08 10] Clear Communication Counters ....................................................................................................... 31

5.3.1.6 [08 12] Return Bus Communication Error Count ......................................................................................... 31

5.3.1.7 [08 13] Return Bus Exception Error Count ................................................................................................... 32

5.3.1.8 [08 14] Return Slave Message Count ............................................................................................................ 32

5.3.1.9 [08 15] Return Slave No Response Count ..................................................................................................... 33

5.3.1.10 [08 18] Return Bus Character Overrun Count ............................................................................................... 33

5.3.2 [17] Report Slave ID.............................................................................................................................. 34

5.4 EXCEPTION RESPONSE DESCRIPTION .......................................................................................................... 35

5.4.1 [01] Illegal Function ............................................................................................................................. 36

5.4.2 [02] Illegal Data Address ...................................................................................................................... 36

5.4.3 [03] Illegal Data Value .......................................................................................................................... 36

6 MODBUS PROTOCOL QUICK REFERENCE ........................................................................................... 37

6.1 PROTOCOL FORMAT .................................................................................................................................... 37

6.2 RTU TRANSMISSION MODE ........................................................................................................................ 37

6.2.1 Coding System ....................................................................................................................................... 37

6.2.2 Serial Byte Setup .................................................................................................................................... 37

6.2.3 Error Checking Field ............................................................................................................................. 38

6.2.4 Message Framing .................................................................................................................................. 38

6.3 ADDRESS FIELD .......................................................................................................................................... 38

6.4 FUNCTION FIELD ......................................................................................................................................... 38

6.5 DATA FIELD ................................................................................................................................................ 39

6.6 ERROR CHECKING FIELD ............................................................................................................................ 39

6.7 FIELD CONTENTS IN MODBUS MESSAGES ................................................................................................... 40