Step 7 instance DBs

Hi
Does the instance data block get updated as the FB is being processed, or does the FB use the local data then update the instance DB at the end of the FB?

Thanks

pp

Paraffin,

I am certain that it gets updated immediately, just as if you were using a regular FC and pointing indirectly to a global DB. An instance DB is just another way of using indirect addressing (sort of).

As a test to verify this, try this: Write a test FB where you change some of the values in the instance DB. Part way through the FB, include a loop that forces the PLC into stop mode before the FB reaches the Block End. Then, change OB 1 so that it doesn't execute any code at all after the re-start. If you then look at the instance DB online, you should see that the values that changed just before the PLC crashed.

I agree with S7Guy.
The instance DBs are manipulated directly from within the FB.

Local data is used for the TEMP variables in both FBs and FCs.
You can see it this way:
Create a TEMP Test BOOL
Then try to assign L0.0 to a coil. STEP7 will exchange L0.0 with #Test .
(assuming that there are no other TEMP variables).