Repeating a task.....SLC 5/04

Can you guys recommend me a way of executing a task every 8 hours on an SLC 5/04 processor.

I've being reading about timers and counters but I've also seen comments about repeat ability and inaccuracy.

Since 8 is a factor of 24, maybe you could use the real-time clock?...



-Eric

Do you know what is the register for the "Real-Time Clock". I was looking and I couldn't find it.

Open the Status data file and look on the right side of the Main tab. Status registers are shown for date and time values. For example, S:40 is the current hour. If you're online with the PLC you can hit the Set Date & Time button to synchronize the clock with your PC.

Create an STI file, configure it to execute once per second (100mS * 10mS). This doesn't use a timer, which is the source of inaccuracies

Put a counter in the file, PREset it to 28800

28800 seconds = 480 minutes = 8 hours

XIO Counter.DN, RETurn from subroutine

So Counter.DN enables the code to execute (don't forget to reset the counter)

If you use the plc internal clock, that can be changed by anyone, anytime.....

Need more help, just ask