Despatch Protocol Plus Modbus Communications - Manual (Page 26)

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.