Cycle Time Overview - Omron CJ2 CPU - REV 10-2010 User Manual

12-2-2 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 Basic I/O Units
• Type and number of Special I/O Units and CPU Bus Units.
• Specific servicing for the following Unit/Boards
• EtherNet/IP tag data link refreshing and the number of tag data link words exchanged
• Data link refreshing and the number of data link words for Controller Link
• Remote I/O for DeviceNet Units and the number of remote I/O words
• Use of protocol macros and the largest communications message
• Socket services for specific control bits for Ethernet Units and the number of send/receive words
• Fixed cycle time setting in the PLC Setup
• File access in file memory, and the amount of data transferred to/from file memory
• Event servicing for Special I/O Units, CPU Bus Units, and communications ports
• Usage of peripheral USB port and serial ports
• Fixed peripheral service execution 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 status 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).
3 The performances of the EtherNet/IP port built into the CJ2H-CPU6@-EIP and the EtherNet/IP port built
into the CJ2M-CPU3@ are very different in terms of data processing for EtherNet/IP tag data links. Refer to
the EtherNet/IP Unit Operation Manual (Cat. No. W465) for details.
The cycle time is the total time required for the PLC to perform the 5 operations shown in the following
tables.
Cycle time = (1) + (2) + (3) + (4) + (5)
1. Overseeing
Checks the I/O bus and user program memory, checks
for battery errors and refreshes the clock.
2. Program Execution
Executes the user program, and calculates the total
time taken for the instructions to execute the program.
3. Cycle Time Calculation
Waits for the specified cycle time to elapse when a min-
imum (fixed) cycle time has been set in the PLC Setup.
Calculates the cycle time.
CJ2 CPU Unit Software User's Manual
Details
Details
Details
12 CPU Unit Cycle Time
Processing time and fluctuation cause
CJ2H-CPU6@-EIP: 0.2 ms
CJ2H-CPU6@: 0.1 ms
CJ2M-CPU1@: 0.16 ms
CJ2M-CPU3@: 0.27 ms
Processing time and fluctuation cause
Total instruction execution time
Processing time and fluctuation cause
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)).
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