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Power OFF Operation Section 10-3
The following timing chart shows the CPU Unit power OFF operation in more
detail.
Power OFF Timing Chart
Power OFF Detection Time
The time it takes to detect power OFF after the power supply falls below 85%
(80% for CJ1W-PD025 DC Power Supply Units or 90% for CJ1W-PD022 DC
Power Supply Units) of the minimum rated voltage.
Power OFF Detection Delay Time
The delay time after power OFF is detected until it is confirmed. This can be
set in the PLC Setup within a range from 0 to 10 ms.
If the power OFF interrupt task is disabled, then the CPU reset signal will turn
ON and the CPU will be reset when this time expires.
If the power OFF interrupt task is enabled in the PLC Setup, then the CPU
reset signal will turn ON and the CPU will be reset only after the power OFF
interrupt task has been executed.
If an unstable power supply is causing power interruptions, set a longer Power
OFF Detection Delay Time (10 ms max.) in the PLC Setup. The CJ1W-PD022
Power Supply Units only support a holding time of 1 ms, however, so this set-
ting is not possible.
Power Holding Time
The maximum amount of time (fixed at 10 ms) that 5 V will be held internally
after power shuts OFF. The time that it takes for the power OFF interrupt task
to execute must not exceed 10 ms minus the Power OFF Detection Delay
Time (processing time after power OFF is confirmed). The power OFF inter-
rupt task will be ended even if it has not been completely executed the
moment this time expires. The CJ1W-PD022 Power Supply Units only support
a holding time of 1 ms, however, so this setting is not possible.
Description of Operation
1,2,3... 1. Power OFF will be detected if the 100 to 120 V AC, 200 to 240 V AC or 24-
V DC power supply falls below 85% (80% for CJ1W-PD025 DC Power Sup-
ply Units or 90% for CJ1W-PD022 DC Power Supply Units) of the minimum
rated voltage for the power OFF detection time (somewhere between 10 to
25 ms for AC Power Supply Units, somewhere between 2 to 5 ms for
CPU reset signal
Stopped
Cyclic tasks or interrupt tasks not
associated with power OFF
Power OFF
detection time:
AC: 10 to 25 ms
PD025: 2 to 5 ms
PD022: 2 to 10 ms
(Power OFF
undetermined)
Power OFF detected Power OFF confirmed
Power OFF
Detection Delay
Time: 0 to 10 ms (set
in PLC Setup)
Operation always stopped at this
point regardless.
Processing time after power
OFF is confirmed: 10 ms
minus Power OFF Detection
Delay Time (PD022: 1 ms
minus Power OFF Detection
Delay Time)
Note: The interrupt task
execution time must be less
than or equal to processing
time after power OFF is
confirmed.
Power OFF
interrupt
task
85% of rated
voltage
(PD025: 80%,
PD022: 90%)
Power OFF
detected signal
Program execution
status
Holding time for 5 V internal power
supply after power OFF detection:
Always 10 ms (PD022: 1 ms)
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