766
FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
34 SFC Program and Step Ladder
34.2 Step Ladder
34.2.3
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