MC68HC908LJ12 Datasheet, PDF (213/413 Pages) Freescale Semiconductor, Inc – 8-bit microcontroller units

Real Time Clock (RTC)
12.4.1 Time Functions
Real time clock functions are provided by the second, minute, and hour
counter registers. All three clock counters are able to generate interrupts
on every counter increment, providing periodic interrupts for the second
(SECF), minute (MINF), and hour (HRF). A CPU interrupt request is
generated if the corresponding enable bit (SECIE, MINIE, and HRIE) is
also set.
12.4.2 Calendar Functions
Calendar functions are provided by the day, day-of-week, month, and
year counter registers. The roll over of the day counter is automatically
adjusted for the month and leap years. The setting for the year counter
ranges from 1901 to 2099.
The day flag (DAYF) is set on every increment of the day counter. A CPU
interrupt request is generated if the day interrupt enable bit (DAYIE) is
also set.
12.4.3 Alarm Functions
An alarm function is provided for the minute and hour counters. When
minute counter matches the value stored in the alarm minute register,
and the hour counter matches the value stored in the alarm hour register,
the alarm flag (ALMF) will be set. A CPU interrupt request is generated
if the alarm interrupt enable bit (ALMIE) is also set.
12.4.4 Timebase Interrupts
In addition to the second, minute, hour, and day periodic interrupts
generated by the clock functions, the divider circuits generates a 2Hz
and a 4Hz periodic interrupt. These are indicated by the TB1F and TB2F
flags. A CPU interrupt request is generated if the corresponding enable
bits (TB1IE and TB2IE) is also set.
Technical Data
214
Real Time Clock (RTC)
MC68HC908LJ12 — Rev. 2.1
Freescale Semiconductor