Modem communication problem AB 5/03 to 5/05

I'm having a problem getting two plc's talking again. The plc's are connected together with two full duplex line driver modems. The master is the AB 5/05 and is configured on chan 0 as half duplex master the other plc is AB 5/03 and appears to be configured as full duplex on chan 0. The problem started out with the AB 5/03 having a fault that damaged some of its memory requiring a saved copy of the program be downloaded, after downloading i recieived the warning message that the chan 0 config in the processor did not match the saved copy i did not apply the saved program half duplex slave setting. After the download everything seemed ok until a check of scada showed no communication with the master 5/05. I replaced both modems and tried again still no luck, then i changed the chan 0 setting to match the saved copy still no luck. Installed a different 5/03 processor downloaded program still have the same problem. Any ideas on how to make sure the 5/03 is configured correctly.

Since the 5/05 has not been changed, it makes the most sense to try to return the 5/03 to the correct settings to match.

Check the 5/05 for MSG instructions and determine what the target node address is, and of course be certain the 5/03 is set for that node number. Examine the MSG instructions for error codes and see if they are simple timeouts or if they indicate a missing source data file or datatype mismatch or something else.

You could also attach a serial analyzer on the 5/03 end to make sure the message requests are getting through the line drivers. Even a simple breakout box will show that there's serial activity.

my distinguished colleague Ken Roach has already given you a logical path to follow ... if that doesn't work, is there any reason why you can't post your program (.RSS) files? ... I'd suggest that you post both the one for the SLC-5/05 and the one for the SLC-5/03 ...

if nothing comes up, I might have time to duplicate your setup in the lab ... maybe something helpful will come from that ...

also ... and this is a LONG shot ... but have you simply tried just powering everything OFF and then powering it all back up again? ... weird as it sounds, in some cases that does the trick ... basic idea: sometimes things "hang up" when those little boxes (SLC and modem) try to talk - but can't for some reason ... a power cycle has been known to "reboot" the system (so to speak) and get things synchronized again ...

I had cycled the power on the modem connected to the 5/03 and downloaded the program again making sure the node address was matching the target address in the 5/05 program. Put the processor back in run and the modem communication started working again. I'm thinking that i had the node addressed incorrectly. Thank you Ken and Ron for your help.