Steve813 (Customer) asked a question.
Why are my Click Plus PLC outputs staying on after changing the program?
Hello, I have a C2-01CPU-2 with C2-14D2 cards installed to the CPU slots. I am just bench testing the PLC for the first time and I noticed something that goes against my understanding of PLC. My program has one ladder rung. I set it to turn on Y021 to look for the output LED on my second IO slot's Output 1. I used an OUT coil. It worked fine. I changed the program's only line of ladder logic to output Y002 instead of Y021 and wrote it to the PLC in runtime mode. Now I have both outputs on (LEDs related to Y002 and Y021). Why should Y021 still be on? t has no output coil that is energized and has even been removed from the program entirely.
This is a great example of why IO should be mapped/buffered. There's nothing telling Y021 to stay energized, but there is also nothing telling it to de-energize. Mapped IO will always have a condition for the physical IO point to see.
I can retry this with mapped/buffer bits and report back.
Most of my CLICK experience is with the older models that did not allow run time editing, so I haven't seen this sort of thing. But if the PLC remained in run mode there wouldn't be anything to tell the output to turn off. However if the the mode was changed to stop then back to run, or the power was cycled, I'm pretty sure the output would turn off. One needs to be somewhat careful about run time edits, if just experimenting it may be best to just stop the PC when uploading
Yeah, cycling through RUN/STOP fixed the issue. Still a weird one to me. Glad I saw that while tinkering just so I didn't scratch my head at this down the road