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FX Series Programmable Controllers Devices in Detail 4
4-5
4.3.3 Special Diagnostic Auxiliary Relays
A PLC has a number of special auxiliar
y
rela
y
s. These rela
y
s all have specific functions and
are classified into the followin
g
two t
y
pes.
a) Usin
g
contacts of special auxiliar
y
rela
y
s
- Coils are driven automaticall
y
b
y
the PLC. Onl
y
the contacts of these coils ma
y
be
used b
y
a user defined pro
g
ram.
Examples: M8000: RUN monitor (ON durin
g
run)
M8002: Initial pulse (Turned ON momentaril
y
when PLC starts)
M8012: 100 msec clock pulse
b) Drivin
g
coils of special auxiliar
y
rela
y
s
- A PLC executes a predetermined specific operation when these coils are driven b
y
the
user.
Examples: M8033: All output statuses are retained when PLC operation is stopped
M8034: All outputs are disabled
M8039: The PLC operates under constant scan mode
4.3.4 Special Single Operation Pulse Relays
When used with the pulse contacts LDP, LDF, etc., M devices in the ran
g
e M2800 to M3072
have a special meanin
g
. With these devices, onl
y
the next pulse contact instruction after the
device coil is activated.
Available devices:
• Not all PLC’s share the same ran
g
e, quantit
y
or operational meanin
g
of dia
g
nostic
auxiliar
y
rela
y
s. Please check the availabilit
y
and function before usin
g
an
y
device.
PLC specific dia
g
nostic ran
g
es and meanin
g
s are available in chapter 6.
4
3
2
5
8
7
6
Turnin
g
ON X0 causes M0 to turn ON.
• Contacts , and are pulse con-
tacts and activate for 1 scan.
• Contact is a normal LD contact and
activates while M0 is ON.
Turnin
g
ON X0 causes M2800 to turn ON.
• Contact is a pulse contact and acti-
vates for 1 scan.
• Contacts and are pulse contacts
of the same M device as contact .
Contact has alread
y
operated, so
contact and do not operate.
• Contact is a normal LD contact and
activates while M2800 is ON.