RLL PLUS
Stage Programming
7–7
RLL
PLUS
Stage Programming
Using the Stage Jump Instruction for State Transitions
The Stage JMP instruction we have used deactivates the stage in which the
instruction occurs, while activating the stage in the JMP instruction. Refer to the
state transition shown below. When contact X0 energizes, the state transition from
S0 to S1 occurs. The two stage examples shown below are equivalent. So, the
Stage Jump instruction is equal to a Stage Reset of the current stage, plus a Stage
Set instruction for the stage to which we want to transition.
S1
X0
JMP
SG
S0
Equivalent
S0
X0
RST
SG
S0
S1
SET
S0 S1
X0
Please Read Carefully – The jump instruction is easily misunderstood. The “jump”
does not occur immediately like a GOTO or GOSUB program control instruction
when executed. Here’s how it works:
S The jump instruction resets the stage bit of the stage in which it occurs.
All rungs in the stage still finish executing during the current scan, even
if there are other rungs in the stage below the jump instruction!
S The reset will be in effect on the following scan, so the stage that
executed the jump instruction previously will be inactive and bypassed.
S The stage bit of the stage named in the Jump instruction will be set
immediately, so the stage will be executed on its next occurrence. In the
left program shown below, stage S1 executes during the same scan as
the JMP S1 occurs in S0. In the example on the right, Stage S1
executes on the next scan after the JMP S1 executes, because stage
S1 is located above stage S0.
S1
X0
JMP
SG
S0
Y0
S1
OUT
SG
S1
S1
X0
JMP
SG
S0
Y0
S1
OUT
SG
S1
Executes on same
scan as Jmp
Executes on next
scan after Jmp
Note: Assume we start with Stage 0 active and stage 1 inactive for both examples.
Stage Jump, Set,
and Reset
Instructions
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