Good morning to all,

in my company we are working in development of devices with MODBUS communication.

Our devices use an owner protocol (in a sub-layer) and after the frame will be translate in MODBUS with an interface. We have a question, related to <b>MODBUS Application Protocol Specification V1.1b3</b>.
At the page 47 - MODBUS Exception Responses, there's a table of Modbus Access Code. In this table are listed the following points:
- 01: illegal function
- 02: illegal data address
- 03: illegal data value
- 04: server device failure
- 05: acknoledge
- 06: server device busy
- 08: memory parity error
- 0A: gateway path unavailable
- 0B: gateway target device failed to respond

There isn't indication about the using of others exceptions code.
In your opinion, the use the others error code (07, 09, 0C, 0D, 0E and 0F) could be correct or is it out of MODBUS standards?

Thank you in advance

 

I had the same problem when I developed a Modbus driver for S7. I then decided for an additional error output parameter in my functions, so that I both comply to Modbus standard and also provide further information to the user.

Just for reference, my drivers manual are here:

http://www.runmode.com/s7xcpmodbus_files/s7xcp_modbus_master.pdf

http://www.runmode.com/s7xcpmodbus_files/s7xcp_modbus_slave.pdf

check the "xCP driver error codes" chapter.

Kind regards
Luca Gallina