dear respectable sir,
iam new instrument engineer and ididn't deal with the (RS232)and other communication protocol, we faced some problems with the communication between the PLC which used to control the compressor and the DCS what's the steps should be done in this case to check it and to decide either the failure from the PLC or DCS or the RS 232.
THANKS ALOT FOR CO-OPERATION.

 

i will suggest if u discribe ur problem in detail so that i can tell u some thing.
let me know what mfp u r using for communication, any interfacing/isolating device b/w plc and DCS is used.more over what happens exactly ??? does serial link alarms appears on ur operater station.