In the FB code accessing the DB data, is it passed into the FB as IN, InOut, or (hopefully not) as Global - which also means and you cannot (strongly should not) use that FB as multi-instance?

Are you checking the (lower and upper) bounds of the UDT array before attempting to read/write from/to it?  If not, you need to add code that checks whether the UDT array index is within the array's bounds, and if not, throw an error.

Do that and you will find your code mistake.  Should not take long to code those changes.

Derek M

I am attempting to track production data through multiple shifts using a shift register based off of a UDT. The shifting is being done through SCL.

I have tested the code itself on a test bench PLC with no issues.

When implementing it on the actual production machine I receive the area length error as soon as the code attempts to access the DB with the UDT array.

The DB is optimized. There is more than enough memory available in the PLC (code work memory 27% used, all others below 5% used).

I originally had the data in retentive memory but tried using volatile when that didn't work. This did not help.

All variables referenced in the FB are declared in the UDT.

I have attached the diagnostic file with the error highlighted.

Any help would be appreciated.