SLC 500 Pogram Disappear!!

Hi All,

I have a SLC 500 controller to run a machine. Few weeks ago, I uploaded the old program from the SLC 500 and did some modification on the program. Later I download the new program to the SLC 500 and the machine ran perfect as I expected. And today I was told that the machine suddenly stopped running. I check on the SLC 500 and find that the program currently in the SLC 500 is the old one. The new program disappear. I re-download the new program to the SLC 500 and the machine can run again.

Does anyone ever deal with this problem before? Is there something I did wrong that may cause the lost of the new program?? Please advise...

P/S: The SLC 500 have an EEPROM memory chip in it and I am sure the new program was downloaded to the SLC500 memory, not EEPROM.

Thanks you very much.


Herbert

Best guess.

The only way that an old program can "suddenly reappear" is if the PLC loaded it from an EEPROM.

The only way that it will load it from an EEPROM is on powerup, or a memory error.

So either the PLC lost power, breifly ("suddenly everything stopped"), or you have grounding issues, which cause the PLC to dump its memory (you might not have noticed this, since the EEPROM would restore the program, and could even put you back in RUN).

I've never encountered this problem before but RSlogix will often match the processor name with the associated program I'm wondering if its done something similar and loaded the wrong source code as a result

I don't know SLC that well but do have experience with PLC-5 EEPROM's.
When I have installed EEPROMS in PLC-5's I would have to specifically burn the program to EEPROM. Then if the program was modified, I then had to re-burn the EEPROM with the modified program otherwise the old program would still be in EEPROM. If a fault then occured such as a total loss of power (including the back up battery) the EEPROM was set to download instantly, which if the EEPROM contained the old program would effectively remove the newer program.

bamatki's statement about the PLC-5's is true for the SLC's also. You must "burn" the EEPROM with your new program. There a number of options for when the EEPROM is read, as shown below

It seem like the problem is related to the EEPROM. I will try again with all the information provided above. Again, Thanks for all your kindly opinion. I appreciate it.

hhuong,

Because you have an EEPROM present, I think that your PLC is loading the old program from the EEProm. It can do this if your new program has an error that causes a Fault. On powerup the next time the old program can be reloaded, if the proper Status bits (S bits) are set to make it do this. To keep it from reloading the old program, you can reset S:1/10, S:1/11, and S:1/12 to 0.

On the other hand, if you want it to reload, then you need to first make sure that your new program has no errors that could cause a fault, then load it to the EEPROM. From the main menu bar, click "Comms", then "EEPROM", then "Store to EEPROM".

or could be possible the old program was reloaded by somebody else.