SOURCE
https://www.eng-tips.com/viewthread.cfm?qid=87845
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QUESTION
I have been programming PLC’s for over three years now. Before I was always taught the KISS (Keep it Simple Stupid) method of including all the safeties and permissives on the output line. I have recently started at a new company, they have a standard of “Five Rung Logic”, I was told it was a GM standard. What are the benefits to this structure? The logic seems cluttered and more confusing to me? Could someone explain why one would benefit from this?
REPLIES
skier
5 rung logic is probably one of the best ways I have seen to standardize programming comprehension between programmers.
Everyone understands
Safety
Precondition
Command
Output
Motion complete
Or some variation of these terms. But always 5 terms.
It increases the total programming required in terms of the number of logic rungs but this increased complexity also makes the program easier for everyone to understand and debug.
You don’t have “decode” someone else’s logic or try to think like them. You don’t just have to rely on “one” guy solely to understand the program. The program is layed out in blocks and subroutines that are easy to follow and and in this manner you are more able to understand how your control process works.
You get the idea.