Multiple OTE

[Jpfleegor]

I have just recently taken a position as a programmer with a company and in one of the processors’ the have an multiple OTE that are the same. They call it reverse logic and it is in many routines and it is set as a controller scope tag. I have set a mock routine in our bench PLC and it acts very odd. Sets itself according to the scan time. Has anyone else seen this or used this. It seems like bad programming. The code is intense so maybe I am missing something though.

 

[DamianInRochester]

What is the code meant to do?

 

[Brijm]

I have just recently taken a position as a programmer with a company and in one of the processors’ the have an multiple OTE that are the same. They call it reverse logic and it is in many routines and it is set as a controller scope tag. I have set a mock routine in our bench PLC and it acts very odd. Sets itself according to the scan time. Has anyone else seen this or used this. It seems like bad programming. The code is intense so maybe I am missing something though.

Most likely, the routines are called, and only one of those ladders is scanned at a time. I would prefer internal bits being used, as AB desperately needs an indication to show if a ladder is being scanned or not. Personally I don't like haveing to jump all over the program, to find which OTE is actually active.

 

[rta53]

I don't think it's a good practice to use real world outputs multiple times in a program. It's certainly allowable as long as you are careful, but I think it creates unnecessary headaches when troubleshooting.

 

[mellis]

Can you show us an example? Guessing about code I've never seen is kind of pointless.

 

[Lare]

I have seen it sometimes to save memory bits on some big programs on old PLC's. Debugging is not easy

 

[lostcontrol]

Why not ask the programmer who did it why?

 

[Liam Moran]

Have any of you worked with the very old Siemens S5 110A?
It was common to use F0.1 as a carry flag multiple times in the program,
Particularly by German programmers.
It was written to in the segment before that containing the output.
Was a b##### to debug.

I have seen the same principle using M0.1 in some S7 code not so long ago.
Incidentally on a German system.