767
FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
34 SFC Program and Step Ladder
34.2 Step Ladder
31
FN
C
275-FN
C
279
Da
ta
Tr
ans
fe
r 3
32
FN
C
280
-F
N
C
28
9
H
igh Speed
Pr
oces
si
ng 2
33
FN
C
290-FN
C
299
Ext
ensi
on Fi
le
R
egi
st
er
34
SF
C
•S
T
L
Pr
o
g
ra
m
m
in
g
35
In
te
rru
p
t
Funct
ion
36
Sp
e
cia
l De
vic
e
37
E
rro
r C
o
d
e
A
V
e
rs
ion U
p
In
fo
rm
a
tio
n
B
Ex
ec
ut
ion Ti
m
e
s
C
Appl
ic
ab
le
In
st
ru
ct
ion Li
st
34.2.4
Creation of step ladder program (SFC program
→
STL program)
The figure on the left shows one state relay extracted as an example from an SFC program.
Each state relay has three functions, driving a load, specifying a transfer destination and specifying a transfer
condition.
The step ladder shown on the right expresses this SFC program as a relay sequence.
In this program, a load is driven, and then the ON status is transferred.
In a state relay without any load, the drive processing is not required naturally.
For the program creation procedure, refer to the description on SFC programs.
→
For the program creation procedure, refer to Subsection 34.1.3.
→
For the handling and role of initial state relays, refer to Subsection 34.1.4.
→
For latched (battery backed) type state relays, refer to Subsection 34.1.5.
→
For RET instruction, refer to Subsection 34.1.6.
*1.
SET and RST instructions for a state relay are two-step instructions.
• When every state relay used in a series of SFC program is programmed without omission, programming is
completed.
• Program a series of step ladder program starting from the initial state relay in the order of state relays
whose ON status is transferred.
Make sure to put RET instruction at the end of a step ladder program.
21
20
Y010
1
X011
X000
TRAN
X010
Y010
STL
S20
Y011
SET
S21
<Step ladder>
<SFC program>
SET
STL
Y011
X010
X011
X001
X000 X001
<List program>
0
1
2
3
4
5
6
7
STL
OUT
LD
OR
OUT
LD
ANI
SET
S20
Y010
X010
X011
Y011
X000
X001
S21
*1
The above program can be expressed in the list format
(list program) as shown on the left.
The portion from STL instruction to RET instruction is
handled as a step ladder program.