RSLogix 5 instucion set

hydin

Member
Join Date
Jun 2002
Location
Lodi CA.
Posts
2
In my logic I have a instruction set(GEQ)that has a branch shunted around it.
I am not sure why this is, does that bypass that instruction set allowing the next instruction set to operate even if the previous one isn't true?
 
Yes it will. And although it's not good practice you'll find it used a lot. Typically, it's used for troubleshooting and forgoten about. Or a quick fix or work around that was never redone correctly.
 
I always make an always on bit and an always off bit with my name in the comment whenever working on a PLC. I disable rungs with the always off bit, and put the always on bit in the shunt around logic I want to bypass. When the process is working and everyone is happy I search for these two bits and take out what ever logic is bypassed or disabled. It's a good way to remind myself what still needs some housekeeping before I leave.
 
I always make an always on bit and an always off bit with my name in the comment whenever working on a PLC. I disable rungs with the always off bit, and put the always on bit in the shunt around logic I want to bypass. When the process is working and everyone is happy I search for these two bits and take out what ever logic is bypassed or disabled. It's a good way to remind myself what still needs some housekeeping before I leave.
Ditto but I only use Always False bit.
 
Good idea. There was a time with Rockwell software that you couldn't search for shorted branches either. Made finding them extremely difficult!
 
I don't use the built in bit because other people may have used and then it leaves with the possibility of thinking that I was the one who made that change when someone else may have actually done and are still tinkering with it. If I have a set of bits that I know only I used it takes that possibility out of the equation.
 
I used to be a senior engineer responsible for the "creation" of large projects, employing a "team" of engineers.

I made sure that I could at least have a stab at policing what was going on.....

1. I banned AFI instructions.

2. I banned shorted branches.

Each programmer had his own "bit" (bit address in SLC/PLC5, tag name in ControlLogix. There was a rung of code that reset/unlatched all of those bits/tags, so they could use XIC (as AFI), and XIO *(as "Always True")

Each day I could cross-ref these flag-bits to see what each programmer needs to work on.

I made them use these flags, and it was as good for them as it was for me - helped to eradicate "forgotten" tweaks, resolutions, rewrites....
 

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