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Quick RSLogix 5000 Question

Quick RSLogix 5000 Question

Quick RSLogix 5000 Question

(OP)
Is there an "ON CHANGE" instruction?  Say, an instruction that watches a value, and goes true when that value has changed?

RE: Quick RSLogix 5000 Question

1 line of logic will work for you

use a NEQ instruction
Value1 not equal to value2, set a bit, branch around bit with a MOV instruction: move value1 to value2.

   

RE: Quick RSLogix 5000 Question

No matter how you do it, you need to allocate one word of memory to store the value from the previous scan.

Assuming you're using the latest version of RSLogix 5k, I think you can actually write your own instruction that takes the watched value and a memory location as parameter.
 

Scott Whitlock
PLC Programming Articles: http://contactandcoil.com/

RE: Quick RSLogix 5000 Question

A DTR Instruction works well. Data Transitional

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