Functions And Operation Examples - Mitsubishi Electric MELSEC FX3U Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
4.4.2

Functions and operation examples

1. General type
S 2
Start
S 20
Lower
limit
S 21
Clamping
S 22
Upper
limit
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 /FX
3U 3UC
PLC.
In FX PLCs, latched type devices are backed up by the EEPROM built into the PLC. When the optional
3G
battery is installed, the battery backs up some general type devices.
• 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.
Initial state
Start
X000
Moving down
Lower limit
X001
Clamping
Clamping
X002
Moving up
Upper limit
X003
PLCs, latched (battery backed) type devices are backed up by the battery built into the
→ For details on backup against power failure, refer to Section 2.6.
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.
TRAN
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.
Y000
When the clamp confirmation limit switch X002 turns
ON, the state relay S22 is set (turned ON).
TRAN
When the operation proceeds to the next step, the
state relay in the preceding step is automatically reset
(turned OFF).
Y001
When the PLC turns OFF, all of general type state
relays are turned OFF.
TRAN
When the ON/OFF status just before power failure is
required, use latched (battery backed) type state
Y002
relays.
TRAN
Ex. Fx
M8002
0
Initial pulse
4 Devices in Detail
4.4 State Relay [S]
X001
S10
/FX PLCs
3U 3UC
FNC 040
S1000
ZRST
S1000 to S1200 are initialized.
1
2
3
4
5
S10
M30
6
Y005
7
8
S1200
9
10
95