shoelesscraig
Member
Ok, so I've got a decent amount of experience working with Logix 5000, but I'm a little fuzzy on the details of something.
I know that Logix 500 processors scan top to bottom and then update outputs. I've got lots of experience there. I also know that the newer Logix 5000 processors do this differently, updating I/O differently.
The other day I ran into a program where someone had written 2 simple rungs. The first moved an integer (say 3 for example) to a DINT. The rung below that moved another integer (say 10 for example) to the same DINT. Both rungs were true, and the DINT had "10" in it. Basically, the last rung won. This is what I expect from a Logix 500 processor, but I didn't think that you could count on the "last rung wins" scenario in Logix 5000...?? So, I'm a little confused.
My guess is that maybe the ladders are still scanned the same way as in 500, top to bottom, and that its just the physical I/O that are updated throughout the scan, but I'm not sure. Can I still program using the "last rung wins" theory in 5000 when my rung is not dealing with physical inputs or outputs?
Somebody school me!
I know that Logix 500 processors scan top to bottom and then update outputs. I've got lots of experience there. I also know that the newer Logix 5000 processors do this differently, updating I/O differently.
The other day I ran into a program where someone had written 2 simple rungs. The first moved an integer (say 3 for example) to a DINT. The rung below that moved another integer (say 10 for example) to the same DINT. Both rungs were true, and the DINT had "10" in it. Basically, the last rung won. This is what I expect from a Logix 500 processor, but I didn't think that you could count on the "last rung wins" scenario in Logix 5000...?? So, I'm a little confused.
My guess is that maybe the ladders are still scanned the same way as in 500, top to bottom, and that its just the physical I/O that are updated throughout the scan, but I'm not sure. Can I still program using the "last rung wins" theory in 5000 when my rung is not dealing with physical inputs or outputs?
Somebody school me!