RS-500 1747-L541 O:6/8 rebooting as true???

Hello fellas... Been a long time.

I'm currently stumped. O:6/8 comes true (on) at every power cycle. For the life of me I can't figure out why. I power up and O:6/8 turns on. I toggle bit to "off" and we good to go, however if power is recycled O:6/8 turns back on.

O:6/8 is only referenced in three locations, once each as OTU, OTL and XIC. Both the OTU and OTL require real world inputs to be present to change. We have all input wires disconnected so there is zero chance that the inputs are seeing a blip on at shutdown. I swapped output cards with same result so its not the card.

It looks like this: (attached)

Have you got an EEPROM installed ?

daba said:

Have you got an EEPROM installed ?

Click to expand...

YES, I've tried disabling that and it seems to save however when I reboot the old setting re-appear negating any changes I tried to make. Even with that I'm not sure why O:6/8 turns on at reboot...

Did you try burning a new image to the EEPROM with those bits set? I guess you would probably want to save the old image first.

No in fact I don't have the equipment to do that. As noted above I have tried to remove it from the boot process. FYI this is a long time fully functional machine program. This could be an anomoly that was never noticed because power was left on 24/7. We were made aware of it and are trying to rectify the situation as quickly as possible.

Can we all agree that the three rungs of logic associated with this bit should not make the bit true on power cycle? If yes I assume we agree that it must somehow be in the mem module (I don't see how yet...). Any ideas how to correct? Is removing the mem module an option??

The machine functions minus this blip which can be "tricked" out to clear. Last thing I want to do is take a chance of causing more issues...

If I am not mistaken, the status bits of the program burned in the EEPROM are what matters. If the program in the EEPROM is set to load on boot, that probably overrides the current program's EEPROM settings.

Here is a bit from the SLC manual:

Set one of the autoload bits S:1/10, S:1/11, or S:1/12 in the status
file of the program in an EEPROM to automatically transfer a
new non-faulted program from the memory module to RAM
when power is cycled.

Click to expand...

Removing the module sounds like a good option as long as you are willing to accept not having the protections it offers such as having the program reload itself on a memory error.

Thanks for the help fellas... I as able to write to memory with the bit off and that solved the "on" at reboot issue...