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RTC_SS
20.3.3.3 Signal Descriptions
Table 20-59 lists the signals and their descriptions for the RTC.
Table 20-59. RTC Signals
Signal I/O Description
RTC_XTALIN I RTC time base input signal. RTC_XTALIN can either be driven with a 32.768-kHz
reference clock, or RTC_XTALIN and RTC_XTALOUT can be connected to an
external crystal. This signal is the input to the RTC internal oscillator.
RTC_XTALOUT O RTC time base output signal. RTC_XTALOUT is the output from the RTC internal
oscillator. If a crystal is not used as the time base for RTC_XTALIN, RTC_XTALOUT
should be left unconnected.
20.3.3.4 Interrupt Support
20.3.3.4.1 CPU Interrupts
The RTC generates two interrupt outputs:
• timer_intr (RTCINT) is a timer interrupt.
• alarm_intr (RTCALARMINT) is an alarm interrupt.
NOTE: Both interrupt outputs support high-level and high-pulse.
20.3.3.4.2 Interrupt Description
20.3.3.4.2.1 Timer Interrupt RTCINT (timer_intr)
The timer interrupt can be generated periodically: every second, every minute, every hour, or every day
(see INTERRUPTS_REG[1:0] for a description of how to set this up). The IT_TIMER bit of the interrupt
register enables this interrupt. The timer interrupt is active-low.
The RTC_STATUS_REG[5:2] are only updated at each new interrupt and occur according to Table 20-60.
For example, bit 2 (SEC) will always be set when one second has passed. It will also be set when one
minute has passed since the completion of one minute also marks the completion of one second (from 59
seconds to 60 seconds). The same holds true for hours and days: each of them will also correspond to the
passing of a second.
Conversely, bit 5 (DAY) will always be set when a day has passed. It might also be set when an hour,
minute, or second has passed. However, this only occurs when the elapsed hour, minute, or second
corresponds to the start of a new day.
Table 20-60. Interrupt Trigger Events
One day has passed One hour has passed One minute has passed One second has passed
STATUS_REG[5] (DAY) 1 0/1
(1)
0/1
(1)
0/1
(1)
STATUS_REG[4] 1 1 0/1
(1)
0/1
(1)
(HOUR)
STATUS_REG[3] (MIN) 1 1 1 0/1
(1)
STATUS_REG[2] (SEC) 1 1 1 1
(1)
This event is only triggered when the elapsed time unit (for example, Day) corresponds to the passage of another unit (for
example, Seconds). For example, when the clock ticks from 00:23:59:59 (days : hours : minutes : seconds) to 01:00:00:00.
3625
SPRUH73H–October 2011–Revised April 2013 Timers
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