Schneider M340 PLC Halt issue

Hi all, been having some trouble with a Schneider M340 PLC halting somewhat seemingly randomly recently. The watchdog timer is being maxed out and getting a "task overrun" message. I've done troubleshooting such as: disabling for loops, disabling sections of logic individually and also checking for divide by zero math. Disabling any one section does not seem to have an effect on PLC halting. Oddly, moving several structured text sections to the FAST (from MAST) task did seem to have a positive effect, but unfortunately I was not able to test on site for a long time, and these changes were removed. This is a setup with several VFDs and a CANopen network. Any insights?

Thank you!

What version of unity are you running.
I had serveral m340's hang up. The only way to get them going again was to power down, remove the sd card, power up so the plc memory is empty then plug sd card in again and redownload.
The problem I found on all of them was using unasigned bool variables on coils. So the plc halted everytime that coil switched on
As soon I gave them an address the problem stopped.
If I remember correctly this was on unity v6

Thanks Chud, It's Unity Pro S V7.0. I'll take a look through the program to check for the coil issue you described.

Just to add. For version 7 there are alot of hotfixes on schneiders website.
If I were you I would also download and install all those hotfixes.Then redownload the program to cpu