779
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
Example of flows with parallel branches and recombination
When the parts A, B and C are processed in parallel and then assembled, flows having parallel branches and
recombination are used.
1. Example of pushbutton type crosswalk
A pushbutton type crosswalk shown in the figure below can be expressed in flows having parallel branches
and recombination.
Y003: Green Y002: Yellow Y001: Red
The SFC program for a pushbutton type crosswalk is as shown below. In this example, a partial flow (jump to
a state relay located in an upper position) is repeated for blinking the green lamp on the crosswalk.
• When the PLC mode is changed from STOP to RUN, the initial state relay S0 turns ON. Normally, the
green lamp is ON for the road and the red lamp is ON for the sidewalk.
• When the crossing button X000 or X001 is pressed, the state relay S21 specifies “road: green” and the
state relay S30 specifies “sidewalk: red”. The signal lamp status is not changed.
• Thirty seconds later, the yellow lamp turns ON for the road. Ten seconds later after that, the red lamp
turns ON for the road.
• When the timer T2 (5 seconds) reaches timeout after that, the green lamp turns ON for the sidewalk.
• Fifteen seconds later, the green lamp starts to blink for the sidewalk. (S32 turns OFF the green lamp, and
S33 turns ON the green lamp.)
• While the green lamp is blinking, S32 and S33 turn ON and OFF repeatedly. When the counter C0 (set
value: 5) turns ON, S34 turns ON. Five seconds after the red lamp turns ON for the sidewalk, the signal
lamps return to the initial state.
• Even if the crossing button X000 or X001 is pressed in the middle of operation, the pressing is ignored.
