Hi, I'm trying to do almost same thing, but only one PLC (Vision 1210). It is Master when comunicating with a rpm driver trough serial. And it is Slave when I try to communicate from software in my laptop trough ethernet (software creates a master instance). PLC works perfect when controlling rpm driver. From laptop to PLC the connection is established (I open a tcp/ip connection using IP and port 502 of PLC and it says "OK" without errors), but when try of read holding registers nothing happens.
I know there are two sources of error: 1) software is not asking properly for the registers.