System Clock; Special Relay Used For System Clock; Special Register Used For System Clock - Mitsubishi Electric MELSEC iQ-R Series User Manual

13.3

System Clock

The system clock is turned on/off by the system or turns on/off automatically at the interval specified by the user.

Special relay used for system clock

Special relay used for system clock are as follows ( Page 652 System clock)
SM number
SM400
SM401
SM402
SM403
SM409
SM410
SM411
SM412
SM413
SM414
SM415
SM420
SM421
SM422
SM423
SM424
SM440
SM441
Precautions
• SM409 to SM415 (System clock) start to measure the time before the CPU module is switched to RUN. Therefore, the time
from the first scan after the CPU module has been switched to RUN until switching of the on/off state of the system clock
may not match the measurement time of the system clock.
• The on/off status of SM409 to SM415 (System clock) changes even during execution of a program. For this reason, when
one program has multiple processes that are performed based on the on/off status of the system clock, these processes
are not performed in the execution order of the program. If these processes are required to be performed in the execution
order of the program, write a program such that the on/off status of the system clock is transferred to an internal relay at the
start of every scan and each processing is performed based on the status in the internal relay.
• In a redundant system, after system switching, SM420 (User timing clock No.0) to SM424 (User timing clock No.4) remain
off in the CPU module of the new control system. To use SM420 to SM424 in the CPU module of the new control system,
execute the DUTY instruction again.

Special register used for system clock

Special register used for system clock are as follows ( Page 684 System clock)
SD number
SD412
SD414
SD415
SD420
13 CLOCK FUNCTION
188
13.3 System Clock
Name
Always On
Always Off
After RUN, ON for 1 scan only
After RUN, OFF for 1 scan only
0.01 second clock
0.1 second clock
0.2 second clock
1 second clock
2 second clock
2n second clock
2n millisecond clock
User timing clock No.0
User timing clock No.1
User timing clock No.2
User timing clock No.3
User timing clock No.4
On only initial I44 execution after RUN
On only initial I45 execution after RUN
Name
One second counter
2n second clock setting
2n ms clock setting
Scan counter