78
FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.4 State Relay [S]
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.
Latched (battery backed) type state relays are backed up by the battery built in the PLC.
→
For the details of each backup method, 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.
3. Annunciator type
Annunciator type state relays can be used as outputs for external fault diagnosis.
For example, when an external fault diagnosis circuit shown in the figure below is created and the contents of
the special data register D8049 are monitored, the smallest number out of the state relays S900 to S999 is
displayed among operation.
If two or more faults have occurred, the smallest state number having a fault is displayed at first. When the
fault is cleared, the next smallest state number having a fault is displayed.
While the special auxiliary relay M8049 is not driven, annunciator type state relays can be used as latched
(battery backed) type state relays in sequence programs in the same way as general type state relays.
In the SFC programming mode in the FX-PCS/WIN(-E), however, S900 to S999 cannot be programmed as a
processes flow in SFC diagrams.
M8002
Initial pulse
FNC 040
ZRST
S1000
S1200
0
S1000 to S1200 are initialized.
M8000
RUN monitor
M8049
Y000
X000
FNC 46
ANS
T 0
K 10
S900
X002
FNC 46
ANS
T 1
K 20
S901
X003
X004
FNC 46
ANS
T 2
K100
S902
M8048
Y010
X005
FNC 47
ANRP
X001
When the special auxiliary relay M8049 is driven,
monitoring becomes valid.
•
If the forward end detection input X000 is not
activated within 1 second after the forward output
Y000 is driven, S900 is activated.
•
The state relays activated by the external fault
diagnosis program can be turned OFF by the reset
button X005.
Every time X005 is set to ON, a state relay having the
smallest number is reset in turn.
If both the upper limit detection input X001 and the
lower limit detection input X002 are deactivated at the
same time for 2 seconds or more, S901 is activated.
•
In a machine whose tact time is less than 10 seconds,
if the switch X004 which is designed to be activated
during one-cycle operation of the machine is not
activated while the continuous operation mode input
X003 is ON, S902 is activated.
•
When either one among S900 to S999 turns ON, the
special auxiliary relay M8048 is activated and the fault
display output Y010 is activated.
•
•
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