Omron CP1H CPU UNITS - PROGRAMMING 05-2007, 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-series Expansion Units and Expansion I/O Units
• Type and number of CJ-series Special I/O Units and CJ-series CPU Bus
Units
• Specific servicing for the following Special I/O Units
• Data link refreshing and the number of data link words for Controller
Link Units
• Remote I/O for DeviceNet 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 num-
ber of send/receive words
• Fixed cycle time setting in the PLC Setup
• Event servicing for CJ-series Special I/O Units, CJ-series CPU Bus Units,
and communications ports
• 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
Details Processing time and fluctuation cause
Checks the I/O bus and user program memory, checks for
battery errors, etc. 0.7 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)).