DeviceNet scanner status problem...


Thread Starter

Slawomir Telman


I have got a little problem with my devicenet network.
I know that a Device net scanner has a status word at the begining of its discrete input. I'm using it to control all the process (if the conditions are false do not allow to start a programm SLC500).

My problem is that: one of the status bits called comunication error is blinking. I mean, if everything is ok that bit should be at zero state but from time to time its changing to logic 1 for just one cycle of PLC. What could be a reason for that kind of situation.

Best regards
Jacek & Slav

Steve Myres, PE

I don't know why it's blinking, but why don't you just wait till the error bit is true for at least three scans before disabling the program?
You might have a network media problem that is causing intermittent errors, enough to cause a scanner error, but not enough to go BUS OFF. You should be able to capture the error by setting a ONS bit with the error bit and move the error code to an integer. Check you network for media problems: proper length, proper terminating resistors, single power supply ground, proper network terminations/connections, no overloading of power supplies, etc.. You might want to see if anyone has a DeviceNet meter in your area to check your network.