Mitsubishi Electronics FX3G User Manual

Page of 964
95
FX
3S
/FX
3G
/FX
3GC
/FX
3U
/FX
3UC
 Series
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.4 State Relay [S]
1
Introdu
ction
2
Ov
ervi
ew
3
Instruction 
Li
st
4
D
evices 
in Det
ai
l
5
Specifi
ed the
De
vice
 &
 
C
onst
ant
6
Bef
ore
 
Pr
og
ra
mmi
ng
7
Bas
ic 
Instruction
8
FN
C00-FN
C0
9
Program Fl
ow
9
FNC
10-FN
C19
Mov
e & Com
pare
10
FNC
20-FNC
29
Arith. & Lo
gi
Operati
on
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
3S
/FX
3G
/FX
3GC
 PLCs, latched type devices are backed up by the EEPROM built into the PLC. When the 
optional battery is installed in FX
3G
/FX
3GC
 PLCs, the battery backs up some general type devices.
→ For details on backup against power failure, refer to Chapter 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 40
ZRST
S1000
S1200
0
S1000 to S1200 are initialized.
Ex. FX
3U
/FX
3UC
 PLCs