A Control.com syndicated community

Modbus Transaction State Diagram
Apr 29, 2008 10:28 pm, by Priya
Subject : Communications
from the Home and Building dept.
Text :
In the Modbus RS485 Communication,

Depending on the result of the processing two types of response can be built:

1. A positive MODBUS response:
the response function code = the request function code

2. A MODBUS Exception response:
if Function Code not supported or Invalid Address or Invalid Data or Error in Processing.

Whether it is mandatory that the Server should provide Exceptional Response if it doesn't support that function code?

What is the standard way of processing a request as per the Modbus Compliance?
Reply