This way, if the timer EVER completed, my debug bit would latch. But that didn't answer the question of why it wasn't working on my S7-1200 demo.Īs a sanity check, my next check was to add a SET coil after my timer to see if the timer was ever completing. To try to prove our theory, we opened up Step7, wrote the same two rungs, and tested it on an S7-300 PLC. I consulted a colleague who believed it should work as well. So as a first attempt at debugging, I deleted the timer, added another, and tried again.
Siemens simatic s7 1200 lldp download#
I first assumed there must be some kind of datablock or download error that had occurred and the timer wasn't executing correctly. However, when testing, I could see that even though the timer seemed to be running AND resetting, my output was NOT being set every second. Once a second, the timer would be "DONE" for one scan and the FB output would be updated. Ordinarily, I would expect this logic to work fine. The two rungs that confounded me and several others are shown below: I was doing a quick test on an S7-1200 PLC (programmed in TIA Portal V13) where I needed to perform a non-time critical operation approximately once a second within a re-usable FB. However, I recently ran across an interesting problem that completely stumped me. if it's IEC61131-3 compliant, I've probably written a few rungs on it.
Siemens, Rockwell, Beckhoff, Mitsubishi, Panasonic. I've done a lot of PLC programming over the last few years.
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