Real-Time Clock
7-174
7.13.2.6
Interrupts Management
RTC can generate two interrupts:
-
Timer interrupt (IRQ_TIMER)
-
Alarm interrupt (IRQ_ALARM_CHIP)
7.13.2.7
Timer Interrupt
IRQ_TIMER interrupt can be generated periodically every second, every
minute, every hour, or every day (RTC_INTERRUPTS_REG[1:0]).
The IT_TIMER bit of the interrupt register enables this interrupt.
The timer interrupt is a negative-edge-sensitive interrupt (low-level pulse
duration = 15
µ
s).
RTC_STATUS_REG [5:2] are only updated at each new interrupt and show
what events have happened, as shown in Table 7–124.
Table 7–124. Timer Interrupts
RTC_INTERRUPTS_REG[1:0]
11
10
01
00
RTC_STATUS_REG[5] (day)
1
0/1
†
0/1
†
0/1
†
RTC_STATUS_REG[4] (hour)
1
1
0/1
†
0/1
†
RTC_STATUS_REG[3] (min)
1
1
1
0/1
†
RTC_STATUS_REG[2] (sec)
1
1
1
1
† 1 when this event is concurrent to programmed periodical period
Figure 7–62 shows IRQ generation waveform.
Figure 7–62. IRQ Generation Waveform
32766
CLK_32KHZ
NIRQ_TIMER
Busy
Timer counter
2
1
0
32767