RSLOGIX5000 COP command not executing

hi,
I have a machine with 2 QR code readers, reading simultaneously, and i am decoding the ascii data from them into DINT for simple label to label matching, all of cam 1's data is being read copied and decoded perfectly, but the logic for cam2 is not acting right. i have boiled the problem down to COP function not executing. it is alone on the rung, i'm copying a string128 to a string128... any help would be greatly appreciated

just a "first try" GUESS ...

you've placed the "problem" rung in a separate/new routine/ladder - and you haven't "called" the new routine with something like a JSR ...

so ... the new routine isn't being "executed" ...

this is a VERY common problem ...

if that doesn't help, consider posting a screen shot of your code and we'll see if we can come up with other suggestions ...

and welcome to the forum ...

Missing JSR could be a cause,

second cause could be the destination is cleared by some other instruction

Could the effect you are seeing be caused if the QR reader Input data was updated in between 32-bit chunks of the COP instruction array ?

Even though the COP instruction is executed completely before the next rung is executed, an I/O update can interrupt the COP instruction's internal array processing.

The quick and dirty solution is to substitute a Copy Synchronous (CPS) instruction for the Copy (COP) instruction, because that locks the source and destination arrays until the whole array is completely copied.

The probability that a basic instruction like COP is "not executing correctly" is zero. The program may not be functioning as you intend, but the instruction is.