Comparing 1 UDT to another (Same UDT Type) In Logix?

Hello,

For sake of discussion;

I have a UDT defined as follows;

UDT1
------------------
Member1 = String
Member2 = DINT
Member3 = DINT
etc. etc.


This is important, I do not want any individual member in the UDT to be part of an array.

Now I create a controller Tag Name MYDATA[10] of type UDT1 (i.e. MYDATA is an array of 11 UDT1's)

I can do.....

COPY MYDATA[1] to MYDATA[2]..... No Problem.

But I can't compare (but I would like to);

If MYDATA[1] = MYDATA[2].

Is there a way to do this or is it not possible with RsLogix 5k (V19)?

Thanks.

I think you will have to compare the individual members of the UDTs to each other.

I agree with Bernie. If you don't like the space that all of the comparisons take up, you could place the comparisons into an AOI.

Alternative

You can also copy the UDT to a DINT array and used ST to do a while loop checking the equality of each DINT. You need to create 2 DINT arrays the same size (or slightly larger) as the UDT. This avoids the need to modify the AOI when you change the UDT, but you'll still need to resize the DINT. The AOI ST can remain unchanged as you just pass in a DINT[1] and check the length. The same AOI would works for any UDT really.


The ladder EQU takes 0.09us vs ST = which takes 0.02, so ST is the way to go for the comparison.
The COP takes 0.02us per DINT, same as the ST = comparison.
So 0.04us x array size (in DINTs, ie bytes/4) is roughly how long a blind check would take.