Ton curiosity

Has anyone seen a timer used like this, one of my guys did this it seems to work just thru me off, always seen timer at the end of the rung?

Logix 5000 has allowed this type of programming since it was first released. After a while it will just seem normal and you will wonder why you can't do it with other packages.

I have always been an advocate of learning all of the tools in a new package. It is very rare that a new tool does not have enhancements that will make your world better.

Do it all the time. One of the things that makes it difficult to then revert back to RSLogix500. It makes for a pretty neat and clean series input debounce.

Only issue I have seen is people confuse the EN output and think that it serves as the DN and then omit to actually put the DN in.

trsptfire said:

Has anyone seen a timer used like this, one of my guys did this it seems to work just thru me off, always seen timer at the end of the rung?

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A couple of our in house guys do this all the time. I personally don't for the very reason you mention.
Plant maintenance staff are the ones that inherhit the controls, so I try and keep logic simple enough to understand.

If there are several occurences of examining of the timer's functional bits within the application it might be beneficial to insert the timer's operand Logix 500 style, at the right end of the rung, however, if there is only one XIC(XIO) of the .dn, .tt, .en bits why not insert it right after the operand?
It is a good practice in comprehending the Logix 5000 ladder logic functionality since I don't believe RA will return to their "old" ways...

curlyandshemp said:

A couple of our in house guys do this all the time. I personally don't for the very reason you mention.
Plant maintenance staff are the ones that inherhit the controls, so I try and keep logic simple enough to understand.

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I hear that argument tossed about now and then.

But can you look at both of these and honestly say you think one is all that more complicated than the other?

In all seriousness, if the maintenance guy can't wrap his head around this maybe he shouldn't be in there anyhow?

DamianInRochester said:

I hear that argument tossed about now and then.

But can you look at both of these and honestly say you think one is all that more complicated than the other?

In all seriousness, if the maintenance guy can't wrap his head around this maybe he shouldn't be in there anyhow?

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Agreed, it is time to throw away the 40 year-old analogy to a hard-wired electrical circuit, and start thinking "logic".

All instructions in A-B controllers are either Conditional, or Non-Conditional, there are no exceptions to this rule.

Conditional instructions test something, and can change the state of the rung/branch from true to false depending on the result of the test. (Note there isn't any way an instruction can change the state from false to true).

Non-Conditional instructions do something, but do not change the state of the rung/branch.

When a person looks at a rung of code, he might look at it as a whole, but the controller doesn't do that - it sequentially processes each instruction with only one input parameter - is the rung currently "true" (the EnableIn).

i can do it in codesys

shooter said:

i can do it in codesys

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Originally posted by shooter:

i can do it in codesys

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I haven't read the spec but I suspect this is something allowed by EN61131. If AB wanted to say they in any way comply with EN61131 they would need to allow this type of construction along with other structure differences. To say L5K is EN61131 compliant is probably a reach. Like I said, I've never read the spec. But the Task/Program/Routine structure of L5K certainly seems more like 3S than Logix500.

Keith

This is a good way to program because it adds to program readability.
But be aware that this will not work with TOF timers though.