RLL PLUS
Stage Programming
7–18
RLL
PLUS
Stage Programming
Our discussion of state transitions has shown how the Stage JMP instruction makes
the current stage inactive and the next stage (named in the JMP) active. As an
alternative way to enter this in DirectSOFT, you may use the power flow method for
stage transitions.
The main requirement is that the current stage be located directly above the next
(jump-to) stage in the ladder program. This arrangement is shown in the diagram
below, by stages S0 and S1, respectively.
S1
X0
JMP
SG
S0
Equivalent
X0
SG
S0
S0 S1
X0
SG
S1
SG
S1
All other rungs in stage...
Power flow
transition
Recall that the Stage JMP instruction may occur anywhere in the current stage, and
the result is the same. However, power flow transitions (shown above) must occur as
the last rung in a stage. All other rungs in the stage will precede it. The power flow
transition method is also achievable on the handheld programmer, by simply
following the transition condition with the Stage instruction for the next stage.
The power flow transition method does eliminate one Stage JMP instruction, its only
advantage. However, it is not as easy to make program changes as using the Stage
JMP. Therefore, we advise using Stage JMP transitions for most programmers.
The Stage View option in DirectSOFT will let you view the ladder program as a flow
chart. The figure below shows the symbol convention used in the diagrams. You may
find the stage view useful as a tool to verify that your stage program has faithfully
reproduced the logic of the state transition diagram you intend to realize.
SG
Stage
Reference to
a Stage
J
Jump
S
Set Stage
R
Reset Stage
Transition
Logic
The following diagram is a typical stage view of a ladder program containing stages.
Note the left-to-right direction of the flow chart.
ISG
S0
SG
S1
SG
S2
SG
S3
SG
S4
SG
S5
J J
J
S
J
Power Flow
Transition
Technique
Stage View in
DirectSOFT
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