Moxa converters

I am looking for documentations concerning the multidrop connection between rs 232 plc.
I am used to connect them (2 or more) by a "MOXA converter A50-A52", but I have often problems with the new version (A52).
The problem is that the Cx, sometimes give me a connection error while I am online with 2 or more Plc';
My test configuration is made :
pc (cx)--moxa(1)---------moxa(2)----------moxa(3)

moxa 2 is connected to a Rs232 Cqm1h
moxa 3 is connected to a Rs232 Cqm1h

The connection between the moxa is done RS422 (4 wires), and also tested as RS485 (2 wires).
I did it without problems by A50 model, but with the same network configuration seems to be impossible to have the same rusults....
If somebody has some suggestions.....


Mike

Yes, it is possible to use RS422 and monitor multiple Omron PLCs. I suspect that the Automatic Data Detect circuit is not reliable. I suggest that you use hardware control (RTS) to switch the transceiver. Here are some modified cuts out of the A52 manual. The pinouts for the cable are for Omron 9Pin serial port.