AB PLC SIM Question

A BIG shout out to all the ones that help everyone here...THANKS!!!


I am running a AB LogixPro Sim and am trying to figure out why the data appears to be changed when it is copied from the “Source File” to the “Dest File” when the “Mask”is set to all ones.
I am using a SQO that is triggered by a TON DN bit and a CTU triggered by the same bit.


The ladder works, my question is that the values before moving are:
N7:1 65534
N7:2 65533
N7:3 65531
N7:4 65527
N7:5 65519
N7:6 65503


The values after moving are:
N7:12 51710
N7:13 51709
N7:14 51707
N7:15 51703
N7:16 51695
N7:17 51679


Why has the data value changed if the “Mask” is set to all 1's


any help would be great


Thanks again,


Echo1515

...why the data appears to be changed when it is copied from the “Source File” to the “Dest File” when the “Mask”is set to all ones.

Click to expand...

The key here is that the Mask has to be set to ALL ONES (or Decimal 65535). Any other number will result in some bits not being passed on. Here is an example of your first 3 values, using the LogixPro Simulator.

It appears that you are using a mask value of C9FF (51711 decimal) rather than "all 1s" which would be FFFF (65535 decimal).

At least that mask value is consistent with the before and after values.

65534 (FFFEh) AND 51711 (C9FFh) = 51710 (C9FE)
65533 (FFFDh) AND 51711 (C9FFh) = 51709 (C9FD)
65531 (FFFBh) AND 51711 (C9FFh) = 51707 (C9FB)
65527 (FFF7h) AND 51711 (C9FFh) = 51703 (C9F7)
65519 (FFEFh) AND 51711 (C9FFh) = 51695 (C9EF)
65503 (FFDFh) AND 51711 (C9FFh) = 51679 (C9DF)

I wonder what was so special about 51711 (C9FF) that made Echo decide to use that number? Maybe his birthday was 1951, July 11?