RSlogix Ladders Parallel or series

Timeismoney08

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• Jun 23, 2013

• #1

Hi all,

When there is multiple ladders in a program, does the PLC scan in parallel or one after another?

 

Eric Nelson

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• Jun 23, 2013

• #2

By 'multiple ladders', do you mean subroutines? If so, then they would be scanned in what you refer to as series. When a subroutine is called, it jumps to that subroutine, then returns to the point where it was called, and continues on.



-Eric

 

Timeismoney08

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• Jun 23, 2013

• #3

Eric Nelson said:

By 'multiple ladders', do you mean subroutines? If so, then they would be scanned in what you refer to as series. When a subroutine is called, it jumps to that subroutine, then returns to the point where it was called, and continues on.



-Eric

Click to expand...

Not Sub routines, Just multiple ladders.

 

Eric Nelson

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• Jun 23, 2013

• #4

Timeismoney08 said:

Not Sub routines, Just multiple ladders.

Click to expand...

Define 'multiple ladders'...



-Eric

 

bernie_carlton

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• Jun 23, 2013

• #5

The scan of multiple ladder rungs (or just rungs) is sequential. This is the primary difference between a PLC and had wired relay control where the effect of all contacts and outputs is simultaneous. Sometimes failing to remember this can lead to problems. At other times knowledge of this fixed sequence can be used to great advantage.

 

Eric Nelson

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• Jun 23, 2013

• #6

bernie_carlton said:

The scan of multiple ladder rungs (or just rungs)

Click to expand...

Aha, rungs! Now the question makes sense.



-Eric

 

dbh6

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• Jun 23, 2013

• #7

@ Timeismoney08 copy and paste the link i provided below into your url and go over section 7.1.2, hope this is what your looking for

http://engineeronadisk.com/V2/book_PLC/engineeronadisk-51.html#pgfId-13356

 

jvdcande

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• Jun 24, 2013

• #8

Time is money: taking the time to read a textbook can generate a lot of money and it doesn't exclude a pint or two on the side.