Odd counter instruction in PLC5

allscott · Jan 20, 2006

I just stubled upon some code that used the .ACC bit of a counter in a XIC instruction. I can't figure out what the programmer was trying to do or when this bit would turn on.

Anyone ever done this?

Ken Moore · Jan 20, 2006

I've seen this before, bit zero will be true for all odd numbers, this can be used to do different things every other count.
Example:
All odd boxes are diverted to line A, all even boxes continue on same line.

russrmartin · Jan 20, 2006

I can't even get the code to accept this in RSLogix 5. What software was this done in. It keeps telling me that it must be set to the bit level, and the with the .acc it can't be done.

garryt1 · Jan 20, 2006

What this means is that the .acc must be followed by a selected bit
e.g T4:0.Acc/0 or T4:0.Acc/1.
Hope this helps you understand.

Ken Moore · Jan 20, 2006

Something like this:

OkiePC · Jan 20, 2006

I've seen the same thing done with a timer to make "flasher" or "blinker" bits:

Bruce99 · Jan 20, 2006

Counter .acc

Ive used this as a flip/flop. C5:22.acc/0 will result in xic changing state with each low to high transition. Ive seen this used as an even/odd type selector. Works very well, and a simple solution to what could be complex code.

allscott · Jan 22, 2006

Yes it appears as though the bit goes "high" whenever the counter is at 0. Still can't figure out what the programmer was trying to do.

Ron Beaufort · Jan 22, 2006

Greetings allscott,

I was doing just fine - right up until you said this:

Yes it appears as though the bit goes "high" whenever the counter is at 0.

and now I’ll admit that I’m a little bit (no pun) confused ...

it seems to me that when the counter’s accumulator is at “0” then all of the bits within the accumulator would have to be “0” or “low” ...

if the counter’s accumulator really-and-truly is at “0” and you’re seeing ANY of the accumulator’s bits (example: C5:0.ACC/0) as a “1” (or as you said “high”), then something is still fishy here ... or am I simply misunderstanding what you meant? ...

maybe it was just a simple typographical error ... if so, don’t worry about it and feel free to ignore this post ... but if you’re really seeing what you said you saw, then please post again with more details ... and is there any reason (proprietary, trade secret, etc.) reason why you can’t post the .RSP program file? ... I’m sure that someone here could help you understand what the original programmer had in mind ...

TConnolly · Jan 22, 2006

Allscot, perhaps then you could post the two rungs, the one in which the counter CTU instruction appears, and the one in which the XIC CX:X.ACC/X appears. Accessing individual bits of the accumulator is a common practice and I'm sure that if we saw the actual rungs we could pin-point it right away.

Odd counter instruction in PLC5

allscott

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