Cycle Time Overview - Omron CS1D DUPLEX SYSTEM - 10-2009 Operation Manual

Computing the Cycle Time
9-4-2

Cycle Time Overview

Normal Processing Mode
Note
344
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, including additional cyclic tasks).
• Type and number of Basic I/O Units
• Type and number of Special I/O Units, CPU Bus Units, Inner Boards, and
type of services being executed.
• Specific servicing for the following Units/Boards
• Data link refreshing and the number of data link words for Controller
Link and SYSMAC LINK Units
• 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, Inner Boards, and
communications ports
• Use of peripheral and RS-232C ports
• Fixed peripheral servicing time in the PLC Setup
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).
Cycle time = (1) + (2) + (3) + (4) + (5)
1: Overseeing
Details
Checks the I/O bus and user program
memory, checks for battery errors and
refreshes the clock.
2: Program Execution
Details
Executes the user program, and calcu-
lates the total time taken for the instruc-
tions to execute the program.
3: Cycle Time Calculation
Details
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.
Section 9-4
Processing time and fluctuation cause
Duplex CPU Systems: 1.9 ms
Single CPU Systems: 0.5 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)).