1756-L8# PLCs - SIZE instruction, using alias as source, rev 16 vs 30

dscish

Member
Join Date
Jun 2019
Location
UK
Posts
17
I've found an interesting issue on some code I've converted from rev 16 to rev 30. The original code has a SIZE instruction with an alias used as the source, the alias being linked to the first element of an array. It seems that in revision 16 this worked ie. returned the size of the aliased array (I can see that as it's passed to a variable in the same rung), but in rev 30 the SIZE instruction returns a 0, ie. it doesn't "translate" the alias and this doesn't see that the source is an array at all.

Any ideas if something got changed in the way SIZE is implemented going from rev 16 to 30? Imho it's bad practice to use an alias in this case, I'd much prefer using the original name of the array (it's first element), but the assumption is to make as little changes as possible to avoid re-testing (clearly in this case it needs to be modified).

Regards,
T.
 

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