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1-3SectionStructure and Operation
16
1-3-5 Cyclic Operation and Interrupts
Initialization processing is performed when the power is turned on. If there are no
initialization errors, the overseeing processes, program execution, I/O refresh-
ing, and communications port servicing are performed repeatedly (cyclically).
Startup initialization
Overseeing
processes
Program execution
Cycle time
calculation
I/O refreshing
RS-232C port
servicing
Peripheral port
servicing
S Check hardware.
S Check memory.
S Read data from flash memory (program,
read-only DM data, and PC Setup settings).
S Check for battery error.
S Preset the watch (maximum) cycle time.
S Check program memory.
S Refresh bits for expansion functions.
S Execute the program.
(Refer to the Programming Manual (W353) for
details on cycle time and I/O response times.)
S Wait for minimum cycle time if a minimum
cycle time has been set in the PC Setup
(DM 6619).
S Calculate cycle time.
S Read input data from input bits.
S Write output data to output bits.
S Perform RS-232C port communications
processing. (Can be changed in DM 6616.)
S Perform Peripheral port communications
processing. (Can be changed in DM 6617.)
PC cycle time
The cycle time can be read from a Programming Device.
AR 14 contains the maximum cycle time and AR 15 contains the present cycle
time in 4-digit BCD.
Basic CPU Operation