Dead Serial port on SLC503

Hello Everyone,

I am wondering if anyone has experienced a faulty serial port on a SLC CPU and if there is any fix (apart from buying a new CPU

I have been able to pinpoint it as the CPU as I can communicate with another CPU with the same cables / hardware etc.

The serial port failed after I was reading values on a excel spreadsheet using a non-AB driver package, does anyone no if this could be relevant.

Regards

Frank

Maybe this will help if you have tried and can't connect using a PIC module either.
See this link on how to reset the processor to factory default, if losing the currently installed program is not a problem.
Link:
http://www.plctalk.net/qanda/attachment.php?attachmentid=5528
Also, click the search button, enter keywords "reset+slc+battery+default" (without the quotes).
If these suggestions don't work , the serial port may be physically damaged or a chip has failed.

You can lock up a serial port with software, but should not be able to damage it. If a power cycle didn't fix it, maybe you somehow changed the port settings. Try the factory default reset method as already suggested, and be aware that a really old SLC can revert to 2400 baud rather than 19.2k.


Paul

I recently had a 5/04 lose comms on the serial port, but only when I enabled the pass-thru bit for the DF1. It would revert to 1200 baud. I found that after upgrading to RSLogix 7.2 and upgrading my Linx package that it was a driver setting that was problematic. I used the KF2 driver and CRC checking. I used a USBS 9300 USB adapter and a CP3 cable to connect at 19200. Shorting out gnd and vbb on the back of the processor is a pain, but it works. I told the A/B tech that they should have installed a switch for that. Good Luck.

I just had a 5/04 that had been running happily along for 9 years with a panelview 900 on the serial port. Trouble call said HMI cannot find a node. Looked at program and all was fine. Replaced panelview but same problem. Replaced cable - same problem. Reloaded program in processor - same problem. Shorted out processor and reloaded program - same problem. Got new processor and loaded program and it works. Now the processor is on my desk waiting for me to either find something wrong or break it completely so it will never work. I have never seen this before so I am glad others have seen serial port problems.

I lost a couple of 5/04 serial ports many years ago, when using roll-around cart-mounted desktop PC and plugging into/out of it with a CP3.

I always suspected electical damage caused by ground potential, but I never bothered to prove it. I just avoided temporary connections on suspiciously grounded PLCs at that plant with a plugged in PC. I used my laptop when absolutely necessary to go "in" CH0.

At my new job we have had it happen to, before I came aboard. My counterpart installed opto-isolators to cure it on our patty forming machines, which are connected thru Digi-1AP boxes to ethernet.
I wonder if the OP was reading values with a temporary connection when the problem occurred?