AB Processor Differences?

Is there any difference between a 1747-L543C Series C FRN 3-6 processor and a 1747-L542B except the L543 has 64k memory and the L542 has 32k memory?

After upgrading to the L543 since we were running out of memory on the L542 we are having strange issues interfacing with a CKD Absodex. Seems like the interface bits that used to come on in sequence are coming on now in the same scan. The start bit is delayed with a 0.01 timer set at 2 after the program select bit comes on but they both appear to come on in the same scan now. This is causing errors on the Absodex controller that we didn't have before.

Does the L543 do anything differently from the L542?

Jerry

can't comment on differences but check your program for...
-excessive CPU scan times
-any faults, minor or major
-program loops, e.g. for next loops (this will raise scan times and slow down PID performance)

The program may be the issue, not the amount of memory...

When we changed the processor we Cycle Stopped the machine and uploaded/saved the PLC program. Swapped processors and downloaded to the new one. It's now running the same program and no faults.

Jerry

How does the average scan time compare between the two CPUs? I suspect the scan time increased a little bit and revealed your issue. You are probably skating on the razors edge using a SLC timer for a 0.01 second delay of a real output...are these real outputs or internal interface bits?

The timers control real outputs. They are devicenet outputs though, not rack I/O.

I've installed the original processor to see if the problem goes away to make sure something else didn't happen at the same time to cause this. I'll let it run for a day and look at production data tomorrow.

Just strange that we never had these faults in the 4 years we've had this equipment and it started on the day we upgraded the processor.

Jerry