Auxiliary Relay [M]; Numbers Of Auxiliary Relays; Functions And Operation Examples - Mitsubishi Electric FX3G SERIES Programming Manual

FX /FX /FX Series Programmable Controllers
3G 3U 3UC
Programming Manual - Basic & Applied Instruction Edition
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. FX /FX PLC
3U 3UC
General type
M0 to M499
*1
500 points
2. FX PLCs
3G
General type
M0 to M383
384 points
*1. This area is not latched (battery backed). It can be changed to a latched (battery backed) area by setting the
parameters.
*2. This area is latched (battery backed). It can be changed to a non-latched (non-battery-backed) area by setting
the parameters.
*3. The characteristics of latch (battery backup) cannot be changed in the parameters.
*4. These registers can be changed to the latched (battery backed) type by the parameter setting when the
optional battery is used. However, the latched range cannot be set.
When simple N : N link or parallel link is used, some auxiliary relays are occupied for the link.
4.3.2

Functions and operation examples

1. General type
M100
NO contact
M100
NC contact
Auxiliary relay circuit
latched (battery backed) Fixed latched (battery
type backed) type
M500 to M1023 M1024 to M7679
*2
524 points
Fixed latched (EEPROM
keep) type
M1536 to M7679
M384 to M1535
1152 points
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
M100
required in control, use latched (battery backed) type auxiliary relays.
Special type
M8000 to M8511
*3
512 points
6656 points
General type Special type
M8000 to M8511
*4
512 points
6144 points
→ Refer to the Data Communication Edition manual.
4 Devices in Detail
4.3 Auxiliary Relay [M]
10
89
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7
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9