Found an OTU with same address used twice, any issue?

[vibbo]

PLC5. Theres an intermittent fault in the plant on auto startup, hunting for address duplicates, noticed an address is assigned to an OTU twice. Apart from being a bit of poor code, it doesnt look like it would have an effect, so Im thinking its probably not an issue, but not sure. Can you confirm? Thanks in advance. Our current guru says he has seen it elsewhere.

 

[Operaghost]

PLC5. Theres an intermittent fault in the plant on auto startup, hunting for address duplicates, noticed an address is assigned to an OTU twice. Apart from being a bit of poor code, it doesnt look like it would have an effect, so Im thinking its probably not an issue, but not sure. Can you confirm? Thanks in advance. Our current guru says he has seen it elsewhere.

Yes, probably poor code, but it isn't the big red flag that two OTE instructions would be. Simply two lines of code that turn off the same output. The two instructions would not "argue" with each other.

OG

 

[harryting]

That's going into philosophical discussion. OTL and OTU is actually designed to be used multiple times. While there are people out there that say to never use latching, I'm on the side that says latching is very useful at times as long as the programmer understand the proper place to use them.

I had a very well functioning sequencer that use all kind of latching. For example, to activate a "Jump to" location I would just latch that bit and the logic that do the jump would then unlatch the activation bit after the Jump.

 

[vibbo]

sweet, thanks.

 

[I_Automation]

Using an OTL you have to think of every situation where you need to OTU it.


E-stop, power loss, safety gate opened, light curtain, cycle interrupt pressed, motor overload, low tank level (or high), overtemp, out of parts, and many, many more.


I have seen one OTL combined with a dozen OTU's on large projects.

 

[James Mcquade]

yes, the latch and unlatch is a useful tool.
unlatching in 2 places is not to difficult to figure out.
the problem is when you latch the same bit in 18 rungs and unlatch it in 24 rungs ! that's poor coding and a pain to debug for maintenance and me as well. No joke, that is exactly the numbers for the latch /unlatch. Paul and I spent 2 days trying to figure out the logic before we gave up and i rewrote the program. Maintenance reviewed the program and we modified it a little, but it was so much easier to work with.
just because you understand the program, the next guy might never figure out.
keep things in simple logic with lots of comments.
james