95
FX
3G
/FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.4 State Relay [S]
1
Int
roduct
ion
2
O
ver
view
3
In
str
uc
tion
Li
st
4
D
evices
in D
etail
5
Spec
ified t
he
D
evice &
C
onst
ant
6
Bef
ore
Pr
ogr
am
m
ing
7
B
asic
In
st
ru
ct
io
n
8
FN
C
00-FN
C
09
P
rogr
am
F
low
9
FN
C
10
-FN
C
19
Mo
ve
&
Co
mp
are
10
FNC2
0-F
NC2
9
Ar
ith.
&
Logic
O
per
ation
4.4.2
Functions and operation examples
1. General type
In the stepping type process control shown in the left
figure, when the start signal X000 turns ON, the state
relay S20 is set (turned ON) and the solenoid valve
Y000 for moving down turns on.
When the lower limit switch X001 turns ON the state
relay S21 is set (turned ON) and the solenoid valve
Y001 for clamping turns on.
When the clamp confirmation limit switch X002 turns
ON, the state relay S22 is set (turned ON).
When the operation proceeds to the next step, the
state relay in the preceding step is automatically reset
(turned OFF).
When the PLC turns OFF, all of general type state
relays are turned OFF.
When the ON/OFF status just before power failure is
required, use latched (battery backed) type state
relays.
State relays have many NO contacts and NC contacts in the same way as
auxiliary relays, and such contacts can be used arbitrarily in sequence
programs.
When state relays (S) are not used for step ladder instructions, they can
be used in general sequences in the same way as auxiliary relays (M) (as
shown in the figure on the right).
2. Latched (battery backed) type
• Latched (battery backed) type state relays store their ON/OFF status even if the power is shut down while
the PLC is operating, so the operation can be restarted from the last point in the process.
In FX
3U
/FX
3UC
PLCs, latched (battery backed) type devices are backed up by the battery built into the
PLC.
In FX
3G
PLCs, latched type devices are backed up by the EEPROM built into the PLC. When the optional
battery is installed, the battery backs up some general type devices.
→
For details on backup against power failure, refer to Section 2.6.
• When using latched (battery backed) type state relays as
general type state relays, provide a reset circuit shown in the
right figure around the head step in the program.
S 2
S 20
S 21
S 22
Start
Lower
limit
Clamping
Upper
limit
Initial state
TRAN
Start
X000
Y000
Moving down
TRAN
Lower limit
X001
Y001
Clamping
TRAN
Clamping
X002
Y002
Moving up
TRAN
Upper limit
X003
X001
S10
S10
M30
Y005
M8002
Initial pulse
FNC 040
ZRST
S1000
S1200
0
S1000 to S1200 are initialized.
Ex. Fx
3U
/FX
3UC
PLCs