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
rela
s. These rela
s all have specific functions and
are classified into the followin
two t
pes.
a) Usin
contacts of special auxiliar
rela
s
- Coils are driven automaticall
b
the PLC. Onl
the contacts of these coils ma
be
used b
a user defined pro
ram.
Examples: M8000: RUN monitor (ON durin
run)
M8002: Initial pulse (Turned ON momentaril
when PLC starts)
M8012: 100 msec clock pulse
b) Drivin
coils of special auxiliar
rela
s
- A PLC executes a predetermined specific operation when these coils are driven b
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
e M2800 to M3072
have a special meanin
. With these devices, onl
the next pulse contact instruction after the
device coil is activated.
Available devices:
• Not all PLC’s share the same ran
e, quantit
or operational meanin
of dia
nostic
auxiliar
rela
s. Please check the availabilit
and function before usin
an
device.
PLC specific dia
nostic ran
es and meanin
s are available in chapter 6.
4
3
2
5
8
7
6
Turnin
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
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
operated, so
contact and do not operate.
• Contact is a normal LD contact and
activates while M2800 is ON.
