Omron SYSMAC CPM2B Operation Manual page 38

Structure and Operation
Program Execution in
Cyclic Operation
Cycle
time
20
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The cycle time will vary slightly depending on the processing being performed
in each cycle, so the calculated cycle time will not always match the actual
cycle time.
The following diagram shows the cyclic operation of the CPM2B when the pro-
gram is being executed normally.
Normally, the results of program execution are transferred to I/O memory just
after program execution (during I/O refreshing), but IORF(97) can be used to
refresh a specified range of I/O words during program execution. The speci-
fied range of I/O words will be refreshed when IORF(97) is executed.
The cycle time is the sum of the time required for program execution, I/O
refreshing, and communications port servicing.
A minimum cycle time (1 to 9,999 ms) can be set in the PLC Setup
(DM 6619). When a minimum cycle time has been set, CPU operation is
paused after program execution until the minimum cycle time is reached. CPU
operation will not be paused if the actual cycle time is longer than the mini-
mum cycle time set in DM 6619.
Note A fatal error will occur and PLC operation will stop if a maximum cycle time
has been set in the PLC Setup (DM 6618) and the actual cycle time exceeds
that setting.
The default settings for RS-232C port servicing and Peripheral port servicing
are 5% of the cycle time, but these settings can be changed (between 1% and
99%) in the PLC Setup. The RS-232C port's setting is in DM 6616 and the
Peripheral port's setting is in DM 6617.
Overseeing processes
Main program
I/O refreshing
RS-232C port servicing
Peripheral port servicing
Section 1-3
If a minimum cycle time has been
set in DM 6619, CPU operation is
paused until the minimum cycle
time is reached.
The servicing time can be set
in DM 6616.
The servicing time can be set
in DM 6617.