JMP Instruction

ghack68695

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Join Date
Oct 2006
Location
GARDEN GROVE,Ca.
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7
I need some advice on what im doing wrong with the JMP instruction. My understanding is that JMP instruction should not be active unless there is an input before it. When I go online with my program I always have an output after the LBL instruction on output O:0/2 even though I never have an input on I:0/1. The JMP instruction does skip rung 0001 as it should but output O:0/2 is always on. I am using a Micrologix 1000 PLC. Any advice would be helpful.
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Your program scans rung 0 and you say rung 1 gets scanned or gets jumped, thats what it should do .
Rung 2 that has the label, is where the program jumps to, and continues the program scan, in your case rung 2 has an unconditional output O;0/2 that is always being told to turn ON.
The program continues to run till it finds an END instruction, then goes thru the whole process again.

If you go to Ron Beauforts site below, and look at his UTube Demos, I feel these will help your understanding
http://www.ronbeaufort.com/

ADDED

I meant to add hover over the instruction in your program and push F1 will give you instruction help
 
Last edited:
Rung 0 - always executed

Rung 1 - executed if I:0/1 is OFF, otherwise it is skipped

Rung 2 - always executed

Rung 3 - always executed

The placement of the LBL (Label) in RSLogix makes it look like a condition. It isn't. It's just a marker and doesn't mean anything during the actual scan of the rung it is on. It would be better if somehow it could be shown to the left over the rung number. But consider that it is essentially an 'always on' bit.
 

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