90 series Micro

[ratcliffe_ic 2]

I have a 90 series Micro PLC that occasionally faults due to a watchdog timer error. (watchdog time exceeded) I'm not sure why it does it and I can't pin it down to any particular event. It can go 6 months with no problem then a spate of faults within a short time. Is there a way to either extend the watchdog timer or ignore it altogether? What if I selected a constant sweep time for the scan? Anybody else experienced problems like this?

[Steve Bailey 118]

What is your program scan time? There is a paragraph on page 8-11 of the Series 90 Micro manual GFK-1065f that may shed some light on your situation. You can get the manual here: http://globalcare.gefanuc.com/ Click on "Product manuals, no login required"

[ratcliffe_ic 2]

Scan time is less than 10mS. Its only a very simple program.

[Steve Bailey 118]

The watchdog error happens when the scan time exceeds 200 mS. If it's happening with a simple program with only the _MAIN program block and no CALL statements or JUMPs to a LABEL earlier in the ladder than the JUMP statement, the next thing I would do would be to make sure I had the latest version firmware. It's been several years since GE Fanuc sold the Series 90 Micro, but check their website to see if you can still download firmware upgrades for it. If bringing it up to the ultimate revision level doesn't cure the problem, and it's more than simply a nuisance, then replace the PLC.

[ratcliffe_ic 2]

Thanks for the advice, I think its time it went to the PLC graveyard!