AB Compact Logix Bool Array in UDT not recognised

Hi Guys,

I couldn’t find any info in the forum to help or explain my issue. Partly because images aren’t working yet…

In the PLC there is a Structure with a Bool[32] under a Program file tags within a UDT

Program File >> UDT >> Bool[32]

I can browse to the Bool array bits using the Quick client but the status of all the bits seems to be common… eg. turn bit[0] on in the PLC and all 32 bits show as ON in Ignition? Changing Bits 1 - 31 have no effect as the bits follow only bit[0].

Creating the UDT directly under Global Tags has the same results.

Creating a Bool[32] under the Global Tags in the PLC works in Ignition as it should…

Creating a Bool[32] under the Program File Tags in the PLC works in Ignition as it should…

So it is just when the Bool array is within a UDT…

Using Ignition both V7.6.6 and V7.6.7 rc2

Any guidance would be appreciated.



After mucking around with this I have moved forward to a degree.

I found I can write to a Bool[32] (inside a UDT) bit by using Bool[0].0, Bool[0].1 … Bool[0].31

However reading from a Bool[32] still has the same issue of only seeing the first bit.

Now using Ignition V7.70

Have you had the same issue with V7.7? We are using v7.7 and are having the same issue you were having - the udt can write to a bit in a word, but it won’t read. To IA; is this something that is going to be fixed within a few days in a minor release, or should we abandon the bit mapping altogether until some future date??



Yes still have the issue of reading individual Bools in V7.7


Hello 0sm0

We recently fixed a bug with the CompactLogix driver where arrays of Bools in a UDT were not showing the correct values for any of the elements. The fix for this bug is available on the most recent 7.7.1 release candidate (7.7.1-rc3).

-You can download the installer here: https://inductiveautomation.com/downloads/beta
-Select 7.7 release candidate
-Download the appropriate installer.

I highly recommend creating a gateway backup before doing any sort of upgrade. The upgrade process should be smooth, but it is always best to have a backup you can restore from should something happen.

If upgrading doesn’t resolve the problem, then please reach out to the support department so we can take a closer look at the issue.


I don’t have the option to test this at the moment but will let you know if any dramas when I do.