75
FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.3 Auxiliary Relay [M]
1
In
troduct
io
n
2
Ov
e
rv
ie
w
3
In
st
ru
ct
ion
Li
st
4
D
evi
ce
s
in
De
ta
il
5
Speci
fied t
h
e
D
evi
ce &
C
onst
a
nt
6
Bef
o
re
Pr
ogr
a
m
m
ing
7
Bas
ic
In
st
ru
cti
o
n
8
FNC0
0
-FNC0
9
P
ro
g
ra
m F
lo
w
9
FNC1
0
-FNC1
9
M
ov
e
&
C
om
par
e
10
FNC
20-
FNC
2
9
Ar
ith.
&
Logi
c
O
per
at
io
n
4.3
Auxiliary Relay [M]
There are many auxiliary relays inside the PLC. Coils of auxiliary relays are driven by contacts of various
devices inside the PLC in the same way as output relays.
Auxiliary relays have many electronically NO contacts and NC contacts which can be used arbitrarily inside
the PLC. However, external loads cannot be driven directly by these contacts. External loads should be
driven by output relays.
4.3.1
Numbers of auxiliary relays
The table below shows auxiliary relay (M) numbers. (Numbers are assigned in decimal.)
*1.
This area is not latched (battery backed). It can be changed to latched (battery backed) area by
setting parameters.
*2.
This area is latched (battery backed). It can be changed to non-latched (non-battery-backed) area by
setting parameters.
*3.
The characteristics of latch (battery backup) cannot be changed by parameters.
When simple N : N link or parallel link is used, some auxiliary relays are occupied for the link.
→
Refer to the Communication Control Manual.
4.3.2
Functions and operation examples
1. General type
All of general type auxiliary relays turn OFF when the PLC turns OFF.
When the ON/OFF status of auxiliary relays just before power failure is
required in control, use latched (battery backed) type auxiliary relays.
General type
latched (battery
backed) type
Fixed latched (battery
backed) type
Special type
FX
3U
/FX
3UC
PLC
M 0 to M499
500 points
*1
M500 to M1023
524 points
*2
M1024 to M7679
6656 points
*3
M8000 to M8511
512 points
M100
M100
M100
NO contact
NC contact
Auxiliary relay circuit