Omron CP1L - 12-2007, Operation Manual

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Computing the Cycle Time
Section 2-7
2-7-2 Cycle Time Overview
The cycle time depends on the following conditions.
• Type and number of instructions in the user program (in all cyclic tasks
that are executed during a cycle, and within interrupt tasks for which the
execution conditions have been satisfied)
• Type and number of CP/CPM1A-series Expansion Units and Expansion I/
O Units
• Use of protocol macros and the largest communications message
• Fixed cycle time setting in the PLC Setup
• Use of USB and serial ports
• Fixed peripheral servicing time in the PLC Setup
Note 1. The cycle time is not affected by the number of tasks that are used in the
user program. The tasks that affect the cycle time are those cyclic tasks
that are READY in the cycle.
2. When the mode is switched from MONITOR mode to RUN mode, the cycle
time will be extended by 10 ms (this will not, however, take the cycle time
over its limit).
The cycle time is the total time required for the PLC to perform the five opera-
tions given in the following tables.
Cycle time = (1) + (2) + (3) + (4) + (5)
1: Overseeing
2: Program Execution
3: Cycle Time Calculation
4: I/O Refreshing
Details Processing time and fluctuation cause
Checks the I/O bus and user program memory, checks for
battery errors, etc. 0.4 ms
Details Processing time and fluctuation cause
Executes the user program, and calculates the total time
time taken for the instructions to execute the program. Total instruction execution time
Details Processing time and fluctuation cause
Waits for the specified cycle time to elapse when a minimum
(fixed) cycle time has been set in the PLC Setup.
Calculates the cycle time.
When the cycle time is not fixed, the time for step 3 is
approximately 0.
When the cycle time is fixed, the time for step 3 is the preset
fixed cycle time minus the actual cycle time ((1) + (2) + (4) +
(5)).
Details Processing time and fluctuation cause
CPU Unit built-
in I/O and I/O
on CP/
CPM1A-series
Expansion
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.