19
Structure and Operation Section 1-3
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.
Program Execution in
Cyclic Operation
The following diagram shows the cyclic operation of the CPM2C when the
program 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 PC Setup (DM 6619).
When a minimum cycle time has been set, CPU operation is paused after pro-
gram execution until the minimum cycle time is reached. CPU operation will
not be paused if the actual cycle time is longer than the minimum cycle time
set in DM 6619.
Note A fatal error will occur and PC operation will stop if a maximum cycle time has
been set in the PC Setup (DM 6618) and the actual cycle time exceeds that
setting.
The default settings for RS-232C and peripheral port servicing are 5% each of
the cycle time, but these settings can be changed (between 0% and 99%) in
the PC Setup. The RS-232C port’s setting is in DM 6616 and the peripheral
port’s setting is in DM 6617.
Refer to Section 7 PC Operations and Processing Time in the Programming
Manual (W353) for more details and precautions on the cycle time.
ime
Overseeing processes
Main program
I/O refreshing
RS-232C port servicing
Peripheral port servicing
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.
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