Step7-Cyclic interrupt time-OB35

[laura]

Hello.

If I set up the Cyclic Interrupt block OB35, to be 50ms........does anyone know, if this time varies........I mean, if there is a tolerance in it, so that in one sample it will be called at fx. 49 ms, and another at maybe 51ms ? Or will the block be called exactly evry 50ms each time ??

 

[PeterW]

I believe it will call at the end of the current block that is processing, which normally be looking at micro seconds.

In your case as there will probably be no code in OB1, the error will be down to the PLC clock accuracy. You can expect more or mess 50ms.

edit: have you ensured that OB35 is to be called every 50ms, do this by looking at the CPU properties in the hardware profile under cyclic interupts.

 

[laura]

Dear PeterW.

Yes I do it in the Hardware Profile, and it is right, that I do not have anything in my OB1.

The only thing I have, is that my OB35 calls my FB10 which, as You know, messes with datablocks.

So You say, that I can expect, that the recording and playing will take event exactly every 50ms ?

 

[PeterW]

yep

 

[Gambrinus]

Yes, it is.