459
Computing the Cycle Time Section 10-4
• Remote I/O for DeviceNet (Master) 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 num-
ber 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 communica-
tions ports
• Use of peripheral and RS-232C 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 5 opera-
tions shown in the following tables.
Cycle time = (1) + (2) + (3) + (4) + (5)
1: Overseeing
Note With CPU22 and CPU23 models, the processing time is 0.6 ms while the
pulse I/O function is used.
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 and refreshes the clock.
CJ1-H-R CPU Unit: 0.13 ms
CJ1-H CPU Unit: 0.3 ms
CJ1M CPU Unit: 0.5 ms (See note.)
CJ1 CPU Unit: 0.5 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)).
To Next Page
Loading...
