SiM3C1xx
4.5.3. Real-Time Clock (RTC0)
The RTC0 module includes a 32-bit timer that allows up to 36 hours of independent time-keeping when used with a
32.768 kHz watch crystal. The RTC0 provides three alarm events in addition to a missing clock event, which can
also function as interrupt, reset, or wakeup sources on SiM3C1xx devices.
The RTC0 module includes internal loading capacitors that are programmable to 16 discrete levels, allowing
compatibility with a wide range of crystals.
The RTC0 output can be buffered and routed to a port bank pin to provide an accurate, low frequency clock to
other devices while the core is in its lowest power down mode. The module also includes a low power internal low
frequency oscillator that reduces low power mode current and is available for other modules to use as a clock
source.
The RTC module includes the following features:
32-bit
timer (supports up to 36 hours) with three separate alarms.
Option for one alarm to automatically reset the RTC timer.
Missing clock detector.
Can be used with the internal low frequency oscillator (LFOSC0), an external 32.768 kHz crystal (no
additional resistors or capacitors necessary), or with an external CMOS clock.
Programmable internal loading capacitors support a wide range of external 32.768 kHz crystals.
Operates directly from VDD and remains operational even when the device goes into its lowest power
down mode.
The output can be buffered and routed to an I/O pin to provide an accurate, low frequency clock to other
devices while the core is in its lowest power down mode.
4.5.4. Low Power Timer (LPTIMER0)
The Low Power Timer (LPTIMER0) module runs from the clock selected by the RTC0 module, allowing the
LPTIMER0 to operate even if the AHB and APB clocks are disabled. The LPTIMER0 counter can increment using
one of two clock sources: the clock selected by the RTC0 module, or rising or falling edges of an external signal.
The Low Power Timer includes the following features:
Runs
on a low-frequency clock (RTC0OSC or LFOSC0 selected in RTC0) or an external source (rising or
falling edge).
Overflow and threshold-match detection, which can generate an interrupt, reset the timer, or wake some
devices from low power modes.
Timer reset on threshold-match allows square-wave generation at a variable output frequency.
4.5.5. Watchdog Timer (WDTIMER0)
The WDTIMER0 module includes a 16-bit timer, a programmable early warning interrupt, and a programmable
reset period. The timer registers are protected from inadvertent access by an independent lock and key interface.
The watchdog timer runs from the low frequency oscillator (LFOSC0).
The Watchdog Timer has the following features:
Programmable
timeout interval.
Optional interrupt to warn when the Watchdog Timer is nearing the reset trip value.
Lock-out feature to prevent any modification until a system reset.
Preliminary Rev. 0.8
41
SILABS [ SILICON LABORATORIES ]
