PLC Program Warnings

bjh said:

This should be addressed as it is at best a troubleshooting nightmare and at worst could cause unexpected machine/process operations.

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Depends on the root cause. Duplicate OTEs yes, but OTL/OTUs will generate this warning, which ends up being just a nuisance.

I also use "Always On-Always Off" bits. OTL, OTU. Comes in handy with my fanuc PMC logic instructions. Not leaving empty rungs leading into blocks.

There are only 2 of us that do the programming where I work.

Mainly Rockwell stuff.

We have a UDT with my name, and my colleagues name with a bunch of bits, DINTS, Reals etc.

That way if I am ever trouble shooting, or modifying code, and can see if my colleague is working on anything and testing stuff.

Cheers

Mark

I am writing the code for a process which has multiple states (operator selects which state) and in 2 or 3 of those states the logic has to do the same thing - say stop motor A. I was trying to implement a routine for each state separately and hence I am getting the duplicate destructive bit warnings. I am now thinking of writing one single ladder logic code for all states in order to remove the warnings - Anybody has better ideas to implement this ?

I am programming a compact logix L33er using rs logix 5000 version 23.

Thanks

As long as I'm understanding you correctly about this sequence.
I would say have a master rung or section to "stop motor A"
All your shutoff conditions will be in parellel with each other or series depending on what devices you are using.

I would say don't try to reuse the same output coil in multiple sections for the same function.

MarkNightingale said:

There are only 2 of us that do the programming where I work.

Mainly Rockwell stuff.

We have a UDT with my name, and my colleagues name with a bunch of bits, DINTS, Reals etc.

That way if I am ever trouble shooting, or modifying code, and can see if my colleague is working on anything and testing stuff.

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When I was in charge of multiple programmers & commissioning engineers on projects, I always had individual BOOL tags with their names or initials.

First rung of the program was an unconditional OTU of all the BOOL tags.

People could use their own "flags", as AFI (XIC), or Branch Shorting (XIO) during development... I completely outlawed AFI's and shorted branches, and would simply delete the if discovered. They were also not allowed to use OTL, OTU, or OTE of their tags.

The benefit of the named tags is that they are easily cross-referenced, to find out what a certain person is yet to complete or correct.

The "software standards" we had to work with utilised multiple OTLs on the same bit, that served as an "OR" function. This of course was flagged up as "Duplicate Destructive Bits", but it was relatively easy to discount them from the verification warnings, as they would be all OTLs with the same names.

daba said:

The "software standards" we had to work with utilised multiple OTLs on the same bit, that served as an "OR" function. This of course was flagged up as "Duplicate Destructive Bits", but it was relatively easy to discount them from the verification warnings, as they would be all OTLs with the same names.

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Some clarification needed here for those just learning RSL5000: Multiple OTLs or OTUs used on a tag will not flag the duplicate destructive bit warning. As soon as an OTE is introduced, the warning is given.

jstolaruk said:

Some clarification needed here for those just learning RSL5000: Multiple OTLs or OTUs used on a tag will not flag the duplicate destructive bit warning. As soon as an OTE is introduced, the warning is given.

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My mistake - its been quite a few years since I worked on those projects, I'm sure it used to give warnings in the early versions of RSLogox5000. If my memory serves me we were on Rev 8 or 9 at that time....

OP....read up on "Mapping" of inputs and outputs.

This is a good way to organize your logic so the physical I/O is only written once in your program.

It also makes it much easier to swap I/O points as you will only need to make a change at one location in your program.

You still have to watch your P's & Q's when writing multiple states as you are doing, but this method will eliminate the warnings you are seeing.

BCS