SLC 5/03 Output Last Sate upon Fault

[NetMan]

This may sound horribly amateurish, but I haven't ever run across this issue with a SLC. PLC-5 yes ... but not a SLC.

I have a SLC 5/03 that once in a blue moon would fault. Sometimes due to an error in the machine's production recipe. Anyway, what happens is when the fault occurs, the outputs are held in their last state and the operator is unable to shut down parts of the process. ALL the SLC's I have will turn OFF ALL outputs when a fault occurs. I've never needed to look at this, until now, with this particular machine. Looking at the process carefully, I can find no reason why the OEM (now out of business) would have set up the SLC to keep the outputs in their last state upon a processor fault condition.

Any assistance in this matter would be greatly appreciated.

- Tony

 

[Lancie1]

There could be a fault-handling subroutine that attempts to recover from a minor fault and keep the process running. Often those fail and leave the processor in an uncontrollable state. Check Status file S:29 to see if there is a subroutine assigned to be the fault-handling routine. If so, look at that subroutine to see which outputs it sets during the fault recovery.

 

[Ron Beaufort]

do these outputs have LOCAL addresses - or do they have REMOTE addresses? ...

specifically, are the outputs that are causing problems located in the SAME chassis with the processor ("local") - or are they located somewhere else? ("remote") ... if remote, please tell us what type of network connection they are using ...

some remote connections are capable of being configured to "reset - turn off" in a fault condition ... others can be configured to "retain their last state" ...

exception: if you have more than one SLC chassis - and these are connected with a simple "expansion cable" we'll need to discuss that separately ... these are (as far as I know) considered to be LOCAL addresses - even though they are not technically located in the SAME chassis with the processor ...

can you post a copy of your program? ... (you'll have to zip it first - forum rule) ...

 

[NetMan]

ok. S:29 is 0

there is an expansion rack, but it's cabled to the main rack. not remote io

still puzzling. i am looking into zipping up the program.

- tony

 

[James Mcquade]

several ideas,
1. Did you look for any MCR conditions?
2. Look at the output word and individual output bits and do a search all and have the globasl search turned on.

the programmer may be turning bits on in a word snd then moving that word to the outputs.maybe a sequencer output.

3. is the plc onterfaced to a panelview terminal or hmi?
in the panel view, you used to be able to set the output on when the panelview booted.

hope this helps,
james