Operating instructions

Reference PTQ-MCM ♦ Quantum / Unity Platform
Modbus Communication Module
ProSoft Technology, Inc. Page 121 of 139
April 29, 2008
00 Return Query Data
The data passed in the request data field is to be returned (looped back) in the
response. The entire response message should be identical to the request.
Sub-function Data Field (Request) Data Field (Response)
00 00 Any Echo Request Data
Example and state diagram
Here is an example of a request to remote device to Return Query Data. This
uses a sub-function code of zero (00 00 hex in the two-byte field). The data to be
returned is sent in the two-byte data field (A5 37 hex).
Request Response
Field Name (Hex) Field Name (Hex)
Function 08 Function 08
Sub-function Hi 00 Sub-function Hi 00
Sub-function Lo 00 Sub-function Lo 00
Data Hi A5 Data Hi A5
Data Lo 37 Data Lo 27
The data fields in responses to other kinds of queries could contain error counts
or other data requested by the sub-function code.