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FX3G/FX3U/FX3UC Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
35 SFC Program and Step Ladder
35.2 Step Ladder
35.2.3 Expression of step ladder
Step ladder programs and SFC programs are substantially the same as described above, but actual programs are
expressed as shown below.
A step ladder program is expressed as relay ladder, but it can be created according to the machine control flow using
state relays.
SET S0
X000
SET S20
STL S20
Process of S0
STL S0
M8002
Start
Y021
Moving
forward
Y023
X001
SET S21
STL S21
Y023
Moving
backward
Y021
X002
SET S22
STL S22
T0
K50
T0
SET S23
STL S23
Y021
Y023
X003
SET S24
STL S24
Y023
Y021
S0
X002
RET
END
It is necessary to input RET
instruction in a program.
Y023
Y021
Ladder block
SFC block
M8002
SET S0
Program for setting to
ON an initial state relay
State number and transfer condition
number are indicated.
0
20
0
1
21
2
22
3
23
4
24
5
S0
RET END
X000
TRAN
Y021
Y023
X001
T0
X002
Y023
Y021
T0
Y021
Y023
X003
X002
RET and END instructions are
automatically written when a program
is input in GX Developer.
K50
TRAN
TRAN
TRAN
TRAN
TRAN
Internal
circuit
<Step ladder> <SFC program>
Start
Can be converted
each other
Moving
forward
Moving
backward
Process of S20
Process of S21
Process of S22
Process of S23
Process of S24
Moving
forward
Moving
backward
Moving
forward
Moving
backward