PLC - VFD communication

[Abdul Wajid]

Dear Folks

Hope everything is good.

One thing surprised me a lot while communicating CP1E-NA PLC & fuji VFD. I was able to successfully communicate PLC & VFD through rs485 and it was working good for read/write command, the problem was

1. Showing communication error in PLC program (A392.12 flag always on), but there wasn't any problem/issue in sending & receiving data bytes

2. Error response byte in D1352 register in PLC shows as normal (00 Hex)  (no com response error).

3. Com error bit A392.12 & execution normal flag A641.01 were ON together while running the application (more surprising for me)

I can't able to figure out the issue for com error bit in PLC which shows ON with running send/receive data. Would it be considered as successful communication even if application is running as per the requirement or still we have to found out the bug and sort out the issue?

 

Thanks

[Abdul Wajid]

In my view which i figure out, the Serial com error bit A392.12 used to store the last condition, so by PLC power cycle the error bit gets off.