Laptop User Manual

S3C2440A RISC MICROPROCESSOR REAL TIME CLOCK
17-3
ALARM FUNCTION
The RTC generates an alarm signal at a specified time in the power-off mode or normal operation mode. In normal
operation mode, the alarm interrupt (INT_RTC) is activated. In the power-off mode, the power management
wakeup (PMWKUP) signal is activated as well as the INT_RTC. The RTC alarm register (RTCALM) determines
the alarm enable/disable status and the condition of the alarm time setting.
TICK TIME INTERRUPT
The RTC tick time is used for interrupt request. The TICNT register has an interrupt enable bit and the count value
for the interrupt. The count value reaches '0' when the tick time interrupt occurs. Then the period of interrupt is as
follows:
Period = ( n+1 ) / 128 second
n: Tick time count value (1~127)
This RTC time tick may be used for real time operating system (RTOS) kernel time tick. If time tick is generated by
the RTC time tick, the time related function of RTOS will always synchronized in real time.
32.768KHZ X-TAL CONNECTION EXAMPLE
The Figure 17-2 shows a circuit of the RTC unit oscillation at 32.768Khz.
XTIrtc
XTOrtc
32768Hz
15~ 22pF
Figure 17-2. Main Oscillator Circuit Example