12 CPU Unit Cycle Time
12-4
CJ2 CPU Unit Software User’s Manual
12-2 Computing the Cycle Time
The CJ-series CPU Units process data in repeating cycles from the overseeing processing up to I/O
refreshing as shown in the following diagrams.
12-2-1 CPU Unit Operation Flowchart
No
Ye s
Ye s
No
Sets error flags
Peripheral
servicing
ERR/ALM indicator ON
or Flashing?
ON (fatal error)
Flashing
(non-fatal error)
Executes user program
(i.e., executes READY
cyclic tasks).
End of program?
Resets watchdog timer and
waits until the set cycle
time has elapsed
Calculates cycle time.
Performs I/O refreshing.
Performs peripheral
servicing.
Check OK?
Checks hardware and user
program memory.
Checks Unit
connection status.
Power ON
Startup
initialization
Overseeing
processing
Program
execution
Cycle time
calculation
I/O
refresh-
ing
PLC cycle time
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