Cyclic Interrupts

adilmahsan

is this time countdown started after every call to the function or after every execution of the function

The time countdown started after every call of the OB not after the full execution of the block.

adilmahsan

if latter is the case, then for a routine in the cyclic interrupt longer than its cyclic time, the block would never be compeletely executed right?

For calling a cycle interrupt we should take care of the followings.

1. When we specify the intervals, make sure that there is enough time between the

start events of the individual cyclic interrupts for processing the cyclic interrupts

themselves. If we assign parameters to deselect cyclic interrupt OBs, they can no longer be

started. The CPU recognizes a programming error and changes to STOP mode.

2. To avoid cyclic interrupts of different cyclic interrupt OBs being started at the same

point and possibly causing a time error (cycle time exceeded) we can specify a

phase offset. The phase offset ensures that the execution of a cyclic interrupt is

delayed by a certain time after the interval has expired.

For example:

Interval = n X basic clock rate 1 ms

Phase offset = m X basic clock rate (where 0 ≤ m < n)

For OB33 the n is 500ms and m is 0

For OB32 the n is 1000ms. And m is 100

The attached doc. Give us a reference.

Regards
ddg