Clearing Array of UDTs

JankyPLC · Feb 22, 2021

Since this is the most helpful place on earth for us programmers, I'm back with another one.

Using Logix v32
I've got an array with 100 elements who's data type are a UDT I created which contains Strings, Dints, and Bools.
I'd like to clear all of the data in this array, but every example I can find online is to populate a value through an array, not a UDT to an array of UDTs.

Obviously the tried and true index loop with a Null Ary CPS is on the table, but is there a cleaner way of accomplishing this?

Thanks in advance!

drbitboy · Feb 22, 2021

The FLL instruction?

Hopes UDTs are treated the same a (control?) structures.

Took me about five tries to get the forum software to put that in caps.

widelto · Feb 22, 2021

Create a tag similar to your udt with empty data (same structure), and copy it 100 times to your array.

plvlce · Feb 22, 2021

If you want to zero everything out, FLL should do the trick.

JeremyM · Feb 22, 2021

widelto said:
Create a tag similar to your udt with empty data (same structure), and copy it 100 times to your array.

You can also zero the first manually, then copy to the remaining elements. This is my preferred way since there's no guarantee (without checking) that the 'zero' UDT is in the initial state.

Nova5 · Feb 22, 2021

alawys Leave UDTTagname(0) empty then you can just mov UDTTagName[0] to UDTTagname[#]. write a little increment logic to increase the # every scan cycle and have it just self clear. 100 element array will take 99 cycles.

Paullys50 · Feb 22, 2021

Nova5 said:
alawys Leave UDTTagname(0) empty then you can just mov UDTTagName[0] to UDTTagname[#].

+1, can also use COP/CPS

rupej · Feb 22, 2021

widelto said:
Create a tag similar to your udt with empty data (same structure), and copy it 100 times to your array.

This is my preferred method. Then just one CPS/COP to clear the whole 100 elements of the original array.

daba · Feb 25, 2021

Nova5 said:
alawys Leave UDTTagname(0) empty then you can just mov UDTTagName[0] to UDTTagname[#]. write a little increment logic to increase the # every scan cycle and have it just self clear. 100 element array will take 99 cycles.

You cannot use MOV with structured tags, you can only use MOV with SINT INT DINT or REAL sources and destinations. Data conversion from one type to another happens automatically.

daba · Feb 25, 2021

rupej said:
This is my preferred method. Then just one CPS/COP to clear the whole 100 elements of the original array.

I would always use CPS over COP if the data is shared with another device, like an HMI or SCADA system, or even another controller as a produced tag.

COP can be interrupted, mid-processing, by the System Overhead Time Slice, or any other task which has higher priority, this means that your "data-set" can become fragmented, half old, half new, data. CPS overcomes that potential problem.

Clearing Array of UDTs

JankyPLC

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