Counter
32kHz
Compensation
Seconds
Minutes
Week
Days
Days
Hours Months
Interrupt
Alarm
Control
Years
RTCALARMINT
RTCINT
32768 Hz
Real Time Clock
timer_intr_pend
alarm_intr_pend
Host ARM
OSC_REG.
SEL_32KCLK_SRC
c32khz_clk
CLK_32KHz
PRCM
CLKIN32
CLK_32K_RTC
RTC_SS
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20.3.3 Functional Description
This section defines the module interrupt capabilities and requirements.
20.3.3.1 Functional Block Diagram
Figure 20-56 shows the RTC module block diagram. Figure 20-57 shows a functional block diagram of the
RTC.
Figure 20-56. RTC Block Diagram
Figure 20-57. RTC Functional Block Diagram
20.3.3.2 Clock Source
The clock reference for the RTC can be sourced from an external crystal (used with the 32K RTC
Oscillator), an external 32KHz oscillator, or from the Peripheral PLL. The RTC has an internal oscillator
buffer to support direct operation with a crystal. The crystal is connected between pins RTC_XTALIN and
RTC_XTALOUT. RTC_XTALIN is the input to the on-chip oscillator and RTC_XTALOUT is the output from
the oscillator back to the crystal. The oscillator can be enabled or disabled by using the RTC_OSC_REG
register. For more information about the RTC crystal connection, see your device-specific data manual.
An external 32.768-kHz clock oscillator may be used instead of a crystal. In such a case, the clock source
is connected to RTC_XTALIN, and RTC_XTALOUT is left unconnected.
The source of the 32-KHz clock is selected using the OSC_CLK.SEL_32KCLK_SRC bit.
If the RTC is not used, the RTC_XTALIN pin should be held low and RTC_XTALOUT should be left
unconnected. The RTC_disable bit in the control register (CTRL_REG) can be set to save power;
however, the RTC_disable bit should not be cleared once it has been set. If the application requires the
RTC module to stop and continue, the STOP_RTC bit in CTRL_REG should be used instead.
3624
Timers SPRUH73H–October 2011–Revised April 2013
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