454
Power OFF Operation Section 10-3
CJ1W-PD025 DC Power Supply Units, and somewhere between 2 to
10 ms for CJ1W-PD022 DC Power Supply Units).
2. If the Power OFF Detection Delay Time is set (0 to 10 ms) in the PLC Set-
up, then the following operations will be performed when the set time ex-
pires.
a) If the power OFF interrupt task is disabled (default PLC Setup setting)
The CPU reset signal will turn ON and the CPU will be reset immedi-
ately.
b) If the power OFF interrupt task is enabled (in the PLC Setup), the CPU
reset signal will turn ON and the CPU will be reset after the power OFF
interrupt task has been executed. Make sure that the power OFF inter-
rupt task will finish executing within 10 ms minus the Power OFF De-
tection Delay Time = processing time after power OFF. The 5-V
internal power supply will be maintained only for 10 ms after power
OFF is detected. The holding time for the internal 5-V power supply of
CJ1W-PD022 Power Supply Units when a power interruption occurs is
1 ms, however, so the Power OFF Detection Delay Time and Power
OFF Interrupt Task Disable functions cannot be used.
10-3-1 Instruction Execution for Power Interruptions
If power is interrupted and the interruption is confirmed when the CPU Unit is
operating in RUN or MONITOR mode, the instruction currently being executed
will be completed (see note 1) and the following power interruption processing
will be performed.
• If the power OFF interrupt task has not been enabled, the CPU Unit will
be reset immediately.
• If the power OFF interrupt task has been enabled, the task will be exe-
cuted and then the CPU Unit will be reset immediately.
The power OFF interrupt task is enabled and disabled in the PLC Setup.
Note 1. The current instruction can be completed only when the time required to
complete execution is less than or equal to the processing time after power
interruption detection (10 ms
− power interruption detection delay time). If
the instruction is not completed within this time, it will be interrupted and
the above processing will be performed.
2. The processing time after a power interruption is detected is 1 ms when a
CJ1W-PD022 is mounted.
Disabling Power Interruption Processing in the Program
With CS1-H and CJ1M CPU Units, if the power OFF interrupt task is disabled,
areas of the program can be protected from power interruptions so that the
instructions will be executed before the CPU Unit performs power OFF pro-
cessing even if the power supply is interrupted. This is achieved by using the
DISABLE INTERRUPTS (DI(693)) and ENABLE INTERRUPTS (EI(694))
instructions.
The following procedure is used.
1,2,3... 1. Insert DI(693) before the program section to be protected to disable inter-
rupts and then place EI(694) after the section to enable interrupts.
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