D V P - E S 2 / E X 2 / S S 2 / S A2 / S X 2 / S E & T P O p e r a t i o n M a n u a l - P r o g r a m m i n g
previous step is completed, therefore it forms a sequential control process similar to SFC
(Sequential Function Chart) mode. The STL sequence can be converted into a PLC ladder diagram
which is called “step ladder diagram” as below.
e
S0
S21
S22
M1002
initial
pulse
M1002
SET
S0
SET
S21
S
S0
SET
S22
S
S21
S
S22
S0
RET
1.5.12 RET (Return)
RET instruction has to be placed at the end of sequential control process to indicate the completion
of STL flow.
e
S
S20
RET
e
S
S20
RET
Note: Always connect RET instruction immediately after the last step point indicated as the above
diagram otherwise program error may occur.
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