4 Monitoring and Computing the Cycle Time
4-4 CP1E CPU Unit Instructions Reference Manual(W483)
The cycle time depends on the following conditions.
•Type and number of instructions in the user program (cyclic tasks and all interrupt tasks for which the
execution conditions have been satisfied)
•Type and number of CP-series Expansion Units and Expansion I/O Units
•Minimum (constant) cycle time setting in the PLC Setup
•Use of peripheral USB and serial ports
Precautions for Correct UsePrecautions for Correct Use
When the mode is switched from MONITOR mode to RUN mode, the cycle time may be extended
by 10 ms (this will not, however, cause a cycle time exceeded error).
The cycle time is the total time required for the PLC to perform the operations given in the following
tables.
Cycle time = (1) + (2) + (3) + (4) + (5)
(1) Overseeing
(2) Program Execution
(3) Cycle Time Calculation for Minimum Cycle Time
(4) I/O Refreshing
4-2-2 Cycle Time Overview
Operation Processing time and
fluctuation cause
Checks the I/O bus and user memory, checks for battery errors,
etc.
0.4 ms min.
Operation Processing time and
fluctuation cause
Executes the instructions in the user program. The time
required is the total of the executions times for all instructions.
Total instruction execution
time.
Operation Processing time and fluctuation cause
Waits for the specified cycle
time to elapse when a minimum
(constant) cycle time has been
set in the PLC Setup.
Calculates the cycle time.
When a minimum cycle time is not set, the time for step 3 is
approximately 0.
When a minimum cycle time is set, the time for step 3 is the
preset fixed cycle time minus the actual cycle time
((1) + (2) + (4) + (5)).
Operation
Processing time
and fluctuation
cause
CPU Unit built-in I/O, CPU
Unit built-in analog I/O (NA-
type only), CP-series Expan-
sion Units and Expansion I/O
Units
Outputs from the CPU Unit to the
actual outputs are refreshed first for
each Unit, and then inputs.
I/O refresh time for
each Unit multiplied
by the number of
Units used.