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RSLogix 5000 “Serial” Logic

RSLogix 5000 allows the use of “serial” logic that does not conform to traditional, electrical ladder logic.

For example, both of the rungs shown below are valid in RSLogix 5000.

Clearly, the second version would not work if wired that way in an equivalent electrical circuit. It would not be allowed in RSLogix 500, either.

The main advantage, in my opinion, to writing the code as it is shown in the second version is that you can get more instructions on the screen, and that involves less scrolling. And, the logic is slightly different; if something turns off the “SystemReady” bit somewhere else in the program, PL1 would not come on.

The main disadvantage, in my experience, is that the second version will drive electricians and maintenance people crazy, if they are not familiar with RSLogix 5000. Their managers will most likely request that you re-write the rung in “traditional” ladder logic.