Siemens plc

Hello everybody!

Has anybody ever experienced that it seems as if the plc does not finish doing everything it is supposed to do within a scan.

I have a program which is using special functions to write to some structs, and the functions are used over and over many times. But sometimes it seems that the functions do not always update the DB'w that it is supposed to write to. Some things in the DB changes, but it is as if the function will not go through all the way....I know it sounds strange, but that is what seems to happen.

And since all the functions gets called from OB1, is there anyway to wait in between the function calls, like say for a second or two. I C programming it is called delay, but I have not seen any similar in S7.

For instance if OB1 was like this:

call fc12
call fc13
call fc22,

If I would like to wait 1 second between each call, anybody know how that can be done??


Thanks alot for any inputs!

brg
Andreas

what kind of special function are you using?

Some system functions are done asynchronously.

Could you not just fit timer conditions to the FC call rung ?
Run timer 1 for 1 sec then timer done call fc12.
Run timer 2 for 2 sec then timer done call fc13
run timer 2 for 3 secs then timer done call fc22.

Post a cut down version of the project that will run and show the problem. (Copy the necessary blocks to a library and archive the library, then attach the zip file to your post)