![]() 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. 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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