APPX
Appendix 4  List of Special Relay Areas
811
A
*1 The following figures show operation examples of SM414/SM415 when a value in SD414/SD415 is changed.
When a value in SD414 is changed from 3 to 10:
(1) The elapsed time after the ON/OFF state of SM414 changes remains.
(2) Value change
SM415 2n millisecond clock • This relay repeats on/off at regular 
intervals specified in units of milliseconds 
on the SD415. (When the value in SD415 
is changed, the elapsed time count that 
has started when the ON/OFF state of 
SM415 last changed continues, and the 
ON/OFF state changes when the new 
specified time is elapsed.
*1
)
• The initial state when CPU module is 
powered on or reset is off.
• This relay switches to on or off after a 
specified time is elapsed even when the 
program execution is in progress.
S (Status change) ALL
SM420 User timing clock No.0 • This relay repeats on/off at specified scan 
intervals.
• The initial state when CPU module is 
powered on or reset is off.
• The on/off scan interval is set using the 
DUTY instruction. (n1: ON scan interval, 
n2: OFF scan interval)
S (Every END) ALL
SM421 User timing clock No.1 ALL
SM422 User timing clock No.2 ALL
SM423 User timing clock No.3 ALL
SM424 User timing clock No.4 ALL
SM440 On only initial I44 execution 
after RUN
• This relay is on during the first execution 
of the inter-module synchronous interrupt 
program (I44) after RUN mode starts and 
off during the second execution onwards.
• Note that the relay status while the DI 
instruction is executed is as follows: On 
during the first execution of the inter-
module synchronous interrupt program 
(I44) after the DI instruction is cleared and 
Off during the second execution onwards. 
(no change after the second DI clear).
• This contact is enabled only for the inter-
module synchronous interrupt program.
S (Power-on to RUN 
or STOP to RUN)
Rn
RnP
RnSF
SM441 On only initial I45 execution 
after RUN
• This relay is on during the first execution 
of the multiple CPU synchronous interrupt 
program (I45) after RUN mode starts and 
off during the second execution onwards.
• Note that the relay status while the DI 
instruction is executed is as follows: On 
during the first execution of the multiple 
CPU synchronous interrupt program (I45) 
after the DI instruction is cleared and Off 
during the second execution onwards. (no 
change after the second DI clear).
• This contact is enabled only for the 
multiple CPU synchronous interrupt 
program.
S (Power-on to RUN 
or STOP to RUN)
Rn
RnP
RnSF
No. Name Data stored Details Set by (setting 
timing)
CPU
n ms
n ms
n1
n2
scan
scan
SM414
SD414
ON
OFF
103
10s
10s3s3s
(1)
(2)