5 function set details – Despatch Protocol Plus Modbus Communications User Manual
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Chromalox Instruments and Controls
A-51643 Rev. 6 10/06/03
20
5 Function Set Details
This section details the Modbus functions supported in the Protocol
TM
Plus controller.
5.1 Function Set Overview
Table 8 Protocol
TM
Plus Function and Exception Code Set
Function Code
Function Name
01
Read Outputs
02
Read Input Discretes
03
Read Holding Register (Read Multiple Registers)
04
Read Input Registers
06
Write Single Register
08
Diagnostics
16
Write Multiple Registers
17
Report Slave ID
Table 9 Protocol
TM
Plus Diagnostic (Function Code 08) Sub-function Set
Sub-function Code
Sub-function Name
Comments
00
Return Query Data
Loop Back
01
Restart Communications Options
Reset the slave. Cancels Listen Only
Mode.
02
Return Diagnostic Register
Contents of slave‘s 16-bit diagnostic
register.
04
Force Listen Only Mode
Reset by Restart Communications
Option
10
Clear Counters and Diagnostic Register
Also cleared at power up. Clears only
the counters
12
Return Bus Communication Error Count
Slave CRC errors only.
13
Return Bus Exception Error Count
Slave Exception Response count.
14
Return Slave Message Count
Number of messages addressed to the
slave and successfully processed.
Includes broadcast messages.