So, I finally got back to the customer with the issue and did some testing.
PLC would not send out any comms related to the chan 0 user port.
did some investigating and scratched the brain of an older tech on rockwell support and found that I was supposed to be seeing a dropdown in the general tab for user/system selection on the channel 0. but this was all grayed out for me. He didn't know why either because he could see it.
Found out that because the upper tab had chan 0 system set to shutdown... it literally just shut down the selection to the port also, and likely the port in general, even though the user tab was active.
Was able to set the chan 0 port to user - ascii - 9600 etc. and started putty up... bam, started seeing commands coming from the plc directly (I had seen some when emulating the processor and chan 0 port, but not from the plc yet).
And after this was known to be firing the right commands out, verified from the ultra 100 manual, and the cable was good. The program was the next culprit. I eventually caught the Ascii write and Ascii read throwing a split second error 0E, or saying that the ACL was clearing it before it could write all the way or something to that effect. Some of this logic had been modified to perform reads and writes and clears based on timers instead of whether they were done/changed.
Had to eliminate whatever logic the previous person years ago had shoved in in some weird attempt to fix something. and suddenly it was working again.
Change of length within the PV, changes the n7 tag, which starts the write/read logic chain to send an index value change to the ultra, and it took it fine finally. Now I'm down to just figuring out why the last person also screwed with an encoder count to activate a cut after feed completes.... which intermittently misses cuts. another years old issue they've just sat on.
So my take is somebody tried to connect, but screwed up the comms, then tried to fix it.... there was no extra ports for communication available. the 5/03 has the drive on the chan 0, and the PV on chan 1 dh485. So somebody must have connected to the chan 0, been unable to get on, then used dh485 without the PV connected. found the channel settings and messed with them until they got it to work by disabling and re-enabling (which sets it to system, not user). After getting online with the PV for control, they probably found that they had a "new" issue to deal with. and tried their best to force the read/write to work without input by adding timers instead of PV inputs to run the logic.... the rest is history.
wow.
