Stop mode detection in S7-200

Hello anyone outthere, does anyone know how to detect that CPU goes from RUN to STOP mode???
Thanx for all replies...

Monitor an output that is turned on all the time in stand alone mode. It will turn off if the PLC stops.

If on a network, send a heartbeat down the network. If the heartbeat stops the PLC has stopped.

I don't have any free outputs...
Yes the PLC is in network with CPU314, to comunicate i use the methods X_GET and X_PUT...

metaller said:

I don't have any free outputs...
Yes the PLC is in network with CPU314, to comunicate i use the methods X_GET and X_PUT...

Click to expand...

You can still roll your own 'heartbeat'

Use the CPU314 to 'put' a value into a location in the S7-200, then in the S7 200 change that value, then when the 314 'gets' that value back it can check that it has changed, if there is no change in value in a set time, then the S7 200 has stopped running.

That is a basic idea which you can expand to suit your application.

Paul

I was thinking more of 2 timers turning on and off a network bit every 2 seconds. Then, a timer at the other PLC reading that bit and resetting a communications time out timer set at say 3 seconds. This would then create an alarm situation "communications lost" if it times out..