1756-DNB card going IDLE

hey!
I have this 1756-DNB card going IDLE for 2-3 seconds and then back to run. It happens every 15 minutes or so...The only thing we've noticed when it happens is that the bit: StatusRegister.Run goes off and StatusRegister.DeviceFailure goes on. We have only 4 PoweFlex 40s on the network and we changed the devicenet modules on all of them and the devicenet card, so far with no luck.
Any ideas?

thanks!

Do you have the correct terminating resistors on each end of the network, if so check all your connections.

Is this a system that was working OK and is now playing up or is it a new system that you are commissioning.

Alan.

thanks for your reply!
it's an old system that has worked well for years, that's why we don't understand how it just started happening all of a sudden...
we also checked all connections and it's all ok