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Chapter 49 Real-Time Clock
4.Registers
When the minute counter overflows, this flag is set to “1”.
• bit10: 1-minute interrupt request flag
• bit9: Enable interrupt requests at 1-second intervals
When the 21 bit down counter is set to “0”, this flag is set to “1”.
• bit8: 1-second interrupt request flag
• bit7-5: Reserved
Be sure to write “0”. The read value is the value written.
• bit4: Undefined
Writing does not affect the operation. The read value is indeterminate.
• bit3: Operation status
• bit2: Update
Before writing “1” to the update bit (UPDT), the hour/minute/second registers must be set to the values with
which to update the hour/minute/second counters. The hour/minute/second registers are updated on
reloading to the 21 bit down counter.
• bit1: Undefined
Writing does not affect the operation. The read value is indeterminate.
• bit0: Start
Application Note: The Sub-second register of the RTC module stores the reload value for the 21bit
prescaler. This value is reloaded after the reload counter reaches "0". When modifying all three bytes, make
sure the reload operation will not be performed in between the write instructions. Otherwise the 21-bit
prescaler loads the incorrect value of the combination of new data and old data bytes. It is generally
INT1
Operation
Read Write
0 No interrupt requests Clear the flag.
1 Generate interrupt requests at 1-minute intervals. Writing does not affect the operation.
INTE0 Operation
0 No interrupt requests
1 Generate interrupt requests at 1-second intervals.
INT0
Status
Read Write
0 No interrupt requests Clear the flag.
1 Generate interrupt requests at 1-second intervals. Writing does not affect the operation.
RUN Status
0 The Real-time Clock module is inactive.
1 The Real-time Clock module is active.
UPDT Status/Operation
0 The update has been completed. (Writing “0” does not affect the operation.)
1
Update the hour/minute/second counters with the values of the hour/minute/second registers,
respectively.
ST Operation
0
The Real-time Clock module stops to operate, and the 21 bit down counter and the hour/minute/second
counters are cleared.
1
The settings of the hour/minute/second registers are loaded to the hour/minute/second counters, and the
Real-time Clock module starts to operate.