M340 hangs!

Hi all
Ive got an installation that is using a M340 plc. They have a alot of power dips which is causing alot of headeaches. My biggest concern is that is would seem that the plc code gets stuck and that certain outputs are maintained even though the code is telling it to stop. Has anyone experienced this with a m340.
After a power cycle on the plc all is well again. When this power dip occurs the plc doesnt switch off as the power supply is still on. But its enough to cause the cpu to go crazy.


Any advise will be app

You can set the failure mode of the output cards to either fallback or maintained, what are they set to, maintain i guess ?

From the M340 manual

At a Glance



This parameter defines the fallback mode adopted by outputs when the PLC switches to STOP due to:

• a processor error
• a rack connection error
• an inter-rack cable connection error

The modes are as follows:

Fallback = Channels are set to 0 or 1 according to the defined fallback value for the corresponding 8-channel group.
Maintenance = The outputs remain in the status they were in before switching to Stop.

Thanks for the advice. Just to let you know there is a error on the bmx ami800 and bmxami810 cards. You can download a fix of the schneider website. The problem is that the anlogue input gets stuck without the plc seeing a fault.
It almost caused a burnt down factory

Cpu run m340

Dear "forumers" I need your priceless help!
I have a modicon M340 plc, installed in a site.
Everything seemed to work ok for over a month till I got a telephone yesterday from the staff there reporting me that the plc have come in STOP mode (green run led flashing).
After I read the M340 manual I found out that this could have happenned from either a

blocking or a non blocking error. In any case as I can see now that there is no way that

someone now can set the plc in RUN state again, other than me travelling again in site and using my laptop right ?
I told the staff to power off and then again on the PLC but in didn't come in RUN state again as I thought it should.
After I checked my project in Unity pro again, I figured out that I haven't checked in the CPU tab properties the field that says "Automatic start in Run", while the "Initialize %MWi on cold start" was checked.
My question is, If I also CHECK "Automatic start in Run" will this mean that in the future after a problem (blocking or non blocking) PLC could come in RUN state again by itshelf without me travelling back in site?
Of course I can understand that I should find out the nature of the error and solve it than keep forcing PLC in run state again and again, but I'm just asking in case I can not find the error's source in short time long.
Sorry if this is a stupid question but .........
Thanks in advance
Dimitris Greece