PLC3 Edit in run mode

[Wize 0]

I was recently trying to edit a PLC3 while it was running, using one of the big industrial terminals. When I tried to insert an instruction or a rung I got the message "I.T. does not have edit resource". The one you normally get when you dont have remote program on or the keyswitch in the wrong position. However, I had remote program activated and the keyswitch was in the position to allow anything, but it wouldnt let me edit the program. I had to knock it into program mode to make my changes (which wasnt too popular with the running plant, but what can you do) Other than 'get a new plc' is there anything I can do next time? Is there some command that I missed to allow edits? Thanks

[jstolaruk 9]

Was there any evidense of a leftover edit someplace else in the logic from a previous session that wasn't assembled? Its been a while since I worked on a PLC3 but something in my memory clicked that I had run into this previously and that was the cause.

[Wize 0]

Ahhhhhh, thats it. I think there was a forced input left on in the system while testing this change. That might have the same effect.

[Wize 0]

Its not working. No pending edits, no forces, key in right position, remote enabled. Still no edit resource. Heeeeeeeeeeeelp

[Ken Moore 23]

I do not have any experience with the PLC-3, but in the PLC-5 if you are out of memory you will get a similar message. How much free memory do you have?

[Wize 0]

Thanks. Trying to hunt down the commands to display free/used memory on the thing to see if thats the problem. Would it be something that is fixable by telling it to repack the memory? (I remember having to do so on Siemens S5) It cant be that short of memory though as the last set of mods that I did added 4 rungs to the program and it didnt let me edit in run before then. The only cure I can think of at the moment is to tap it hard with a very big hammer (and get a new one in)

[Guest Guest]

This message also normally appears when one terminal is connected and a second one comes on line. Only one can have the edit resource at a time. Is the 'ACCESS' light on the processor front panel lit? Sounds like a glitchy thing where the processor mistakenly thinks a terminal is hooked up when that is not actually the case. I'm unsure if this will help but, can you check a system status bit? Specifically: status file 0, word 3, bit 05. PLC-3 manual definition - The processor sets this 'remote' bit when a remote device controls the operating mode. This bit remains set until the device releases control. Remote device control can be overridden by a local device such as the industrial terminal or front panel.

[Wize 0]

Via the industrial terminal, bit 5 is off. Bits 4 and 6 of the same word are on. I have two identical PLCs (with their own terminals) hooked up in a dual arrangement running the same program. So if its a hardware fault, its happened to them both at the same time. They have also been power cycled to no avail. <wonders if an oil soaked rag and a lighter may solve all the problems>

[Guest Guest]

There may be some help here I've found that sometimes the actual state of edits is not reflected in the "EDITS" status box in the software (AI series). That is, after assembling edits, the display still shows that edits exist. This can sometimes be cleared by assembling edits again - at least it's worked for me.

[Gerry 13]

Is this a redundancy setup? If so, there are significant restrictions to what you can do on-line. I wish I could remember more precisely...it was such a long time ago.

[Wize 0]

This is set up so you are able to turn off one PLC at a time to be able to modify it. However, due to some extra 'safty' curcuitry round the system, they have the ability to power themselves, or each other, off. It has done so randomly while turning one PLC off or into program mode (as demonstrated last time I worked on one of them) so I cant risk putting on of them into program mode while they are controling plant production (or people get quite angry)