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Explanations of PLC Setup Settings Section 7-2
The following table shows a breakdown of the peripheral servicing time.
The default value for each servicing process is 4% of the last cycle’s cycle
time.
In general, it is recommended that the default value be used. Set a uniform
servicing time only when peripheral servicing is being delayed because each
service process is being spread over several cycles.
Note 1. When the peripheral servicing time is set to a time longer than the default
value, the cycle time will also be longer.
2. The fixed peripheral servicing time setting cannot be changed while the
CPU Unit is in RUN mode or MONITOR mode.
3. Use the Peripheral Servicing Priority Mode to give priority to servicing pe-
ripheral over program execution.
Power OFF Interrupt Task This setting determines whether or not a power OFF interrupt task will be exe-
cuted when a power interruption is detected. (When this setting is set to 0, the
regular program will just stop when a power interruption is detected.)
The power OFF interrupt task will be stopped when the power hold time (pro-
cessing time after power interrupt + power OFF detection delay time) has
elapsed. The maximum power hold time is 10 ms.
When a power OFF detection delay time has to be set, be sure that the power
OFF interrupt task can be executed in the available time (10 ms – power OFF
detection delay time).
Note The power OFF interrupt task setting cannot be changed while the CPU Unit
is in RUN mode or MONITOR mode.
Power OFF Detection
Delay Time
This setting determines how much of a delay there will be from the detection
of a power interruption (approximately after the power supply voltage drops
below 85% of the rated value) until a power interruption is established and the
regular program is stopped. The setting can be between 0 and 10 ms.
It takes a maximum of 10 ms for the internal 5-V DC power supply to drop to
0 V DC after the initial power interrupt detection time. Extend the time until
detection of a power interruption when momentary interruptions in a bad
power supply are causing PLC operation to stop.
Peripheral servicing time Default value Setting range
Event service time for
Special I/O Units
4% of the previous
cycle’s cycle time
Uniform servicing time in ms:
0.0 to 25.5 ms in 0.1-ms units
Event service time for
CPU Bus Units
Same as above.
Event service time for
peripheral port
Same as above.
Event service time for
RS-232C port
Same as above.
File access service time for
Memory Card
Same as above.
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