Jump To Label (Jmp); Relay Ladder - Allen-Bradley Logix5000 Reference Manual

Program Control Instructions (JMP, LBL, JSR, RET, SBR, JXR, TND, MCR, UID, UIE, AFI, NOP, EOT, SFP, SFR, EVENT)

Jump to Label (JMP)

Label (LBL)
Description:
Arithmetic Status Flags:
Fault Conditions:
The JMP and LBL instructions skip portions of ladder logic.
Operands:

Relay Ladder

Operand
JMP instruction
Label name
LBL instruction
Label name
When enabled, the JMP instruction skips to the referenced LBL instruction and
the controller continues executing from there. When disabled, the JMP
instruction does not affect ladder execution.
The JMP instruction can move ladder execution forward or backward. Jumping
forward to a label saves program scan time by omitting a logic segment until it's
needed. Jumping backward lets the controller repeat iterations of logic.
Be careful not to jump backward an excessive number of times. The watchdog
timer could time out because the controller never reaches the end of the logic,
which in turn faults the controller.
The LBL instruction is the target of the JMP instruction that has the same label
name. Make sure the LBL instruction is the first instruction on its rung.
A label name must be unique within a routine. The name can include the
following:
· Have as many as 40 characters
· Contain letters, numbers, and underscores (_)
Not affected
A major fault will occur if
Label does not exist
Rockwell Automation Publication 1756-RM003N-EN-P - October 2011
Type Format
Label name
Label name
ATTENTION: Jumped logic is not scanned. Place critical logic
outside the jumped zone.
Fault type
4
Description
Enter name for associated LBL instruction
Execution jumps to LBL instruction withreferenced
label name
Fault code
42
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