S7 1200 OB1_PREV_CYCLE

Hello Alex.

Sorry to say - I am not following what you are trying to show me. I am not trying to be difficult either.

My suggestion: run an IEC_TIMER and the implimented code in parallel. Compare the results of these. Even running V3 and V4 in parallel should show a difference.

I am known to make mistakes. But my prediction is that the V4 code will loose up to 75ms (very variable) every 85.9s.

The STOPWATCH code I included (see link above) is based on the lessons from V3. The zip file I added to the Forum has two SCL files. One also includes the testing method used to confirm the working of STOPWATCH. Several insightful comments are included inside the SCL code also.

Bye.
- Dan

Hello Dan,

You were right. A measurement for two hours at a minimum cycle time of 75ms gave me a -40s deviation. For me this part is clear.

At this moment (and for the last couple of days) I'm testing your STOPWATCH in several ways. Some unexplained things I've seen so far. Nothing to worry about on your side.

The results I will post in your RUNTIME topic.

Regards,
Alex

Hello Alex.

Valuable feedback. Thank you. It will be interesting to see your results in the STOPWATCH code.

On a personal note - You do know I did not budget to pay you a salary this month - right? (joke)

Do me one favour and for the sake of others downloading our codes: Please make a note on your V4 code that there is an issue. I am just worried that the guys will try using the code without reading our conversations.

"Good doing business with you."
 - Dan

Hi Dan,

I thought it was better to remove the attachment, so I did.

Haha, no for me it's easy. It's called: multitasking... It's just a matter of changing some parameters and let the program run for an hour. Now it's an investment of lets say 20 hours, but it will safe me a lot of struggles in the future. Otherwise I have to say to the costumer it’s a bug. We programmers know that a bug is really in most cases a programming mistake.

The pleasure is all mine.

Regards,
Alex

Hello.

The following attachment contains the latest version of code that was shared earlier. For more detail see also:
https://support.industry.siemens.com/tf/ww/en/posts/s7-1200-runtime-instruction-problem-with-possible-workaround/165149/?page=0&pageSize=10#post676480

Regards.

Hello, dP!

In looks like internal counter maximum value equals to 13FFFFFFFF (hex), which is 85899345919 (dec).

So your OVERFLOW constant may be made more precise.

OVERFLOW : LReal := LREAL#85.899345919;

 Let's save 19 ns for the better future!