I am fairly new with using GE plc's . I am using a IC693CMM311 communication module using both ports in RTU mode in a application and would like to know if there is an easy way to monitor when i lose communications with the external device. Are there some sort of status bits for this?
Thanks

I don't recall anything off the top of my head, but I'm shure there is something in the manual.  It can be found at http://globalcare.gefanuc.com

The manual is GFK-0582.

That is pretty standard that the operator interface requests and posts information to the PLC without any intervention from the PLC program.  There probably is a status indicator to let you know that communication is active.  It may be hardwired, but it probably does some type of status bit.  I would have to look that up; however, the best way to handle checking communication loss either between PLC's or a graphic interface from the  PLC side is to work up some sort of heartbeat between the two devices.  In a PLC to PLC communication, this would require setting up a timed bit toggle that would be transmitted to the other PLC.  The other PLC would check the heartbeat bit to make sure it is cycling as required.  This would also work with your situation.  The operator interface could be programmed to toggle a bit at a predetermined rate and the PLC could check that.  This is an unusual circumstance as most operator interfaces have some way to indicate a communication loss to the operator.  Generally if you lose the operator interface, you lose the ability to operate the system and indication is necessary to let the operator know.  Your situation is unusual as you want to detect on the PLC side to be able to take action.  You mention  that nothing in the registers will change.  Are you just referring to the fact that the operator cannot enter setpoints or something else?

Russell