Allen Bradley PLC heartbeat logic

I have been upgrading our communications between PLCs within the mill. We finally got rid of the last DH+ comms and I am now cleaning up programing, setting up better interlocks between machine centers, etc... I recently learned how to use DTR instruction for heartbeat detection instead of comparing and moving words. My question is, does anyone have a better way to generate the heartbeat values (such as a single instruction). I currently add '1' to a word each scan then compare value and clear it before it goes out of range. It only requires three instructions on one rung but a single instruction would be neater.

You might want to try looking at the internal clock, I look to see if the clock keeps changing.

i don't quiet understand your statement.
a heartbeat signal is typically between to or more plc's.
we use heartbeat signals between plc's and wonderware to ensure the process is running and to alarm when its fsulted.

regards,
james

I just run a timer in the destination PLC and MSG instruction from the source PLC continuously resets the timer. If the timer times out comm is assumed to be lost.

I suppose that there are hundreds of ways to do a heartbeat.