According to my text  book exercise these program (attached by picture) must act like this: These codes are written in OB1. Why after download these program is no problem for a while but after that, CPU go to STOP mode?

I test these program by PLCSIM. But it is functioning very strange. RLO is not function normal in that comparator. And CPU never go to STOP !! And after the first time RUN if I do STOP_RUN again or do COLD RESTART, the value of the MW0 is set to 1000 instead of zero (0) . Why???!!!

Even after MRES , the MW0 value is not ZERO (0)?!! What the hell ?!

Hasan Sabbah

Hi Hasan,

perhaps you can explain what it is that you are trying to achieve.  Looking at the code, what I see is that you have created a loop that will count to 1 000 and then exit, but all in one scan. Online display might have difficulty in showing what is happening.

fritz

Hasan Sabbah

If you try this with PLCSIM you will see that the logic does not work like you said. it count until 32767 and the go negative.

But of course it will as that is what you programmed it to do (i.e. count to 1000 in MW0 in the first OB1 scan, then to 2000 in the second OB1 scan and so forth)

 Not exactly every scan it will count 1000. Because in this program it will increment mw0 until 1000 only first scan then every scan mw0 will be incremented by 1 until 32767. And that's why Hasan said when restart PLC, MW0 start at 1000. But in reality mw0 start at 0 and after first scan it reaches 1000