PLC2 Program Addressing

I am modifying a program and there is a cross reference that is confusing.
There is a rung where the only operation is a GET PUT instructions where the PUT is address 377. The rung references 477 which is a counter in a WORD TO FILE move in another rung. I know that the preset for 477 is stored in 577 and the accumulated value is 477. Why would the rung that contains 377 reference 477? 377 is not used any where else.
Can anyone clear this up for me.
Thanks

plc2 addressing

You are more than a little confused. The cross referencing information at the end of a rung points you to other rung numbers where the instructions in that rung are used.(in your example the rung number is 477 which is not an address) The addresses for the GET's and the PUT's have nothing to do with cross reference rung numbers. They only tell the processor where to GET the data and where to PUT it. Look at the problem from this perspective.
Randy

I know how to read the addressing info. It list both the address number and the rung number. 477 is the address and it list the rung number next to it (341).
My question has address 377 in the rung and list 477 in rung 341 as a cross reference for 377.

plc2 addressing

Well! I am at a loss to help on this one! Maybe one of the other folks that frequent this site will be more helpful than I can be.
Good luck!!
Randy

Since the '2' is obsolete, this is, at best, an academic exercise.
It would help to know what software printed the listing. In the
early days, when they went from PLC 2 to PLC 2/20 to PLC 2/30,
the data table got expanded, and sometimes the offline documentation
programs did not keep up.

Specifically, I remember when UPDOC was confused by an output to
address 20000. (200/00). It thought the address was an operand,
and the output looked like -(/)-|.

You've likely uncovered some such thing.

Since the '2' is obsolete, this is, at best, an academic exercise.

Click to expand...

But there are still quite a few 2's out there, chugging right along.

No this is no exercise, just becasue someone doesn't make a product anymore doesn't mean that it stops existing.
It is a PLC2/30 and was printed from one of those old operator inerface machines.

I think the cross ref lists 477 with 377 because thet are related--one preset--one acc value--of a counter/timer. If you look at a PLC-5 or SLC-500 cross ref, it list all used references to a timer/counter in the same place--i.e acc value, preset value, done bits, tt bits, etc.

<<I'm Not Dead Yet>>

the previous poster has a point, and a very valid one. The
PLC-2 is not dead. The PLC-2 was a wonderful product, for
the market it was developed for, and with the technology
available at the time.

My point was that, to my knowledge, no company is actively
developing or supporting software tools for the PLC-2 family
processors, at least none that I know of.

Finding the software problem that incorrectly prints cross
references is a wonderful thing. Reporting it to someone
who might be able to fix it...that's something else.


<<with appolgies to Monty Python fans everywhere>>