Hello,

I am working on a system where a non-siemens PLC is communicating with Masterdrive VC Port X300 via RS232C null modem cable over USS protocol. Each telegram consists of total 20 bytes (including STX, LGE, ADR, BCC and net data).

Now I am communicating non-siemens PLC with CP341(RS232C). I am using CP341 example project as a reference in STEP7. I am sening and receiving telegrams in CP341 without any errors. But the HMI is showing Serial Communication Error!!! The HMI is connected to the non-siemens PLC.

Please find attached my STEP7 project and Masterdrive backup.

Kindly help what am I missing? Is there some timings issue? Is there a problem in block calls? Any other issues?

Waiting for comments.

Reagrds,