Un Supported Function Code-3 and Function Code-64 Message

[jouharn]

We are receiving a warning message of Unsupported function Code 3&64 in a network monitoring device (Nozomi). Source and Destination devices are Modicon M580 PLC. Modbus Communication between 2 PLCs are done using Read var /Write Var function blocks.

The warning is getting reported occasionally.  What could be the issue?

[RoozeeR]

Hello,

Can you check in the source M580  (Ip.7 and IP.8) how the read functions are programmed, either with READ_VAR or with DATA_EXCH functions?

The error on FC64 seems normal to me because as far as I know it's not implemented in M580. The only way to create FC.64 in an M580 is using a DATA_EXCH function, which makes possible to create a "free form" message in the PLC logic. but the M580 destination will answer with an "unsupported" reply.