AB PLC2/30 shift register syntax

Unregistered · Jun 29, 2005

Hi,
Im trying to remember old PLC2/30 syntax for a shift register.
Specifically:
What is [G], [=] and (PUT)??
Thanks

randylud · Jun 29, 2005

WOW, a blast from the past!

G is for GET, = is for, well, equals and PUT is just what it says it is. In the old days of AB, you had to GET the data you were going to work with, work with it however you needed to and then you had to PUT it some place. A rung might have looked like this:

 

     140        150       141     142                165

-----[G]--------[=]-------[G]-----[+]--------------( PUT )---

The rung above would translate as: Get the value at address 140 and see if it is equal to the value in 150. If it is equal, then Get the value in 141 and add it to the value in 142 and put the result of the addition in address location 165.

I am sure glad we are past that point these days. As for shift register instructions for the old 2/30, I never used one and actually would not believe that there was one but you could have probably come up with some rungs of code that would have achieved the same result. A lot of work to do very little in those days.

Unregistered · Jun 29, 2005

Thanks, How about 1 more?

Thanks very much!!!

I follow (I'm actually a little long in the tooth myself).

Next question, what is (SCT).

Thanks in advance!!!

randylud · Jun 29, 2005

No clue on the SCT but a suggestion, why not register and become a regular member here with us other long in the toothers? We have some fun and learn some things too!

Doug-P · Jun 29, 2005

randylud wrote: As for shift register instructions for the old 2/30, I never used one and actually would not believe that there was one but you could have probably come up with some rungs of code that would have achieved the same result. A lot of work to do very little in those days.

The PLC-2/30 in addition to bit shift registers includes shift file up (SFU) and shift file down (SFD) instructions.

SCT is a scan counter. This counter will increment each scan that the ladder conditions are true. It resets when the rung is false. Sort of a mutant TON.

randylud · Jun 29, 2005

Thanks, Doug, I knew someone would be able to help on those other things!

Gerry · Jun 30, 2005

randylud said:
Get the value in 141 and add it to the value in 142 and put the result of the addition in address location 165.

Actually, that would look like this:



      141       142               165

  ----[G]-------[G]---------------(+)--

(+) and (PUT) are both output instructions - only one output allowed per rung.
Generally not a good idea to use the 100 addresses for arithmetic since they would either be part of the input image table or presets for timers and counters.

Unregistered · Jun 30, 2005

Thanks Guys!!!
You apparently have better memories than I!

AB PLC2/30 shift register syntax

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randylud

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randylud

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Doug-P

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randylud

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Gerry

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