Understanding a RS Logix 500 MOV Instruction

Good Afternoon ,

I am trying to understand a MOV instruction . This is suppose to keep track of the layers on a palletizer .

Line 4
Current Layers

MOV

Move
Source N102:[N7:11]
6
Dest N102:101
6
What do you think is going on with N102:[N7:11] . Are these two merging somehow ? N102 is the data file for layers , and N7 is just labeled as a Integer Data file. What is the normal practice for something like this.....

Move
Source N102:[N7:11]

Thanks in advance,

If N7:11 is 4, then you'd move the value of N102:4 to N102:101

If N7:11 is 4, then you'd move the value of N102:4 to N102:101

Sorry for my dumbness , but what tells me "If N7:11 is 4" ?

see if this helps ...

http://www.plctalk.net/qanda/showthread.php?p=632294&postcount=23

Rob S. said:

If N7:11 is 4, then you'd move the value of N102:4 to N102:101

Sorry for my dumbness , but what tells me "If N7:11 is 4" ?

Click to expand...

The PLC logic. Somewhere in your program the value in N7:11 is being manipulated or written to.
Do a search for that address. If you can't find it, post your program here (zip it first) and someone will help.

Rob S. said:

If N7:11 is 4, then you'd move the value of N102:4 to N102:101

Sorry for my dumbness , but what tells me "If N7:11 is 4" ?

Click to expand...

It's inserting the value of N7:11 into N102:[x]. Since you have N102:[N7:11], if the value of N7:11 is 4 you'll get N102:4. If the value of N7:11 is 10, you'll get N102:10.

EDIT: Whoops, think I misread the question

Thanks . Attached is the file. Thanks Ron for the link. Are you still doing classes ?

I've taken a QUICK look through your file (all I have time for right now) and I don't see any "obvious" point where the value of N7:11 is being manipulated by the ladder logic ...

GUESSING HERE: but is there another processor - or maybe an HMI - connected to this system which might be "pushing" a value (for example: 76) into the N7:11 location - over a network connection, etc. ? ...

this is pretty common for some palletizers - where another (usually larger) processor - or an operator - is keeping track of the "layers" or other positions to be "picked up from" - or "placed into" ...

you might want to post a more updated copy of the program file ... this one is a "backup" version - and (worse) it doesn't have any descriptions in it ... any descriptions available MIGHT offer a clue as to where the value contained in N7:11 is actually coming from ...

Thanks Ron for the link.

Click to expand...

glad to help ...

Are you still doing classes ?

Click to expand...

yes ... but I'm already booked solid out into October ... my little wife is letting me go "just one more year" before retiring - but she only lets me teach one week a month now (instead of my usual two or three weeks per month) ... frankly I'm going nuts thinking about being "fully retired" soon - but I'm pretty sure that this one is the very last year ...

I don't see anything in the program. (others may)

HMI? SCADA system? Something connected to one of the comm ports?

Edit: Ron types faster.

Yes. It is an HMI . This processor keeps track of all the patterns and then sens the pattern , layers , number , etc. to 3 palletizers.