S7-200 as Modbus Slave with ABB PLC (Comm. Module CI853)

[mtariq_amin]

Dear All,

I trying to establish Modbus Communication between ABB (Communication Module CI853 & CPU PM861A---AC800M) and S7-200 (CPU 226) PLC’s.

S7-200 was working OK as a slave with Modbus simulator.
Also ABB was working OK as Master with Modbus Simulator.
But together, ABB and S7-200 are not communicating.
There is Send and receive light blinking on ABB communication module but they are saying that they are not getting any response from Slave (Its giving time out error).


The distance between S7-200 and ABB PLC is only 5 meter.

Our settings are 9600,8,1,Even Parity.

We tried to Lower the Baud rate to 4800, but it didn't work.
The confusion is that both PLC's are working fine with simulator but they are not communicating together.

I am only dealing with S7-200, and there are only 2 networks to configure it as a slave. But why its not giving response to ABB.

Between ABB and S7-200 PLC, there is WESTERMO Modem (MDW45) for conversion from RS-232 to RS-485 (since ABB port is RS232 and our port is RS485).

We also checked WESTERMO dip switch settings and they are OK.
Kindly help me out on this issue.

Regards,
Tariq

 

[vip1400]

Dear Mr.Tariq,
actually I am not familiar with [FONT=&quot]AC800M from A BB only we use ABB _ AC450 i think you need to make sure to use the right RS-485 connections between both CPU and you have to do the right s/w configuration
also if there is any deep switches in the Communication Module CI853card you have to configure it[/FONT]