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CHAPTER9 DEVICES
9
2
3
4
5
6
7
8
9.
 I
n
te
rnal Us
er Dev
ice
9.
2.
 I
n
te
rnal relay (M)
9
 
-
 
9
9.2.3  
Internal relay (M)
(1) Definition
The internal relay (M) is a device for auxiliary relays used in the CPU module.
All of the internal relay are set to off in the following cases:
 • When the CPU module is powered off and then on
 • When the CPU module is reset
 •
When latch clear is executed
 (
(2) Latch (data retention during power failure)
The internal relay cannot be latched.
(3) Allowable number of 
normally open or closed contacts
There are no restrictions on the number of normally open or closed contacts used in a program, as 
long as the program capacity is not exceeded
.
(4) Method for external output
The output (Y) is used to output sequence program operation results to external devices.
Use the latch relay (L) when latch (data retention during power failure) is required.
(
Figure 9.9 Internal relay (M) used in a program
X0
M0
TO
Y20
X1 M0
M100
X2 M0
M2047
SET
M0
K20
No restrictions on the quantity used.
M0 is set to on when X0 turns on from off.
Internal relay (M0) can be set to on only for 
use inside the CPU module, and  not for 
output to the outside.
The on/off information of M0 is output from the 
output module to the external device.