C8051F960-B-GM Datasheet, PDF (295/492 Pages) Silicon Laboratories – Ultra Low Power 128K, LCD MCU Family

C8051F96x
24. SmaRTClock (Real Time Clock)
C8051F96x devices include an ultra low power 32-bit SmaRTClock Peripheral (Real Time Clock) with
alarm. The SmaRTClock has a dedicated 32 kHz oscillator that can be configured for use with or without a
crystal. No external resistor or loading capacitors are required. The on-chip loading capacitors are pro-
grammable to 16 discrete levels allowing compatibility with a wide range of crystals. The SmaRTClock can
operate directly from a 1.8–3.6 V battery voltage and remains operational even when the device goes into
its lowest power down mode. The SmaRTClock output can be buffered and routed to a GPIO pin to provide
an accurate, low frequency clock to other devices while the MCU is in its lowest power down mode (see
“PMU0MD: Power Management Unit Mode” on page 267 for more details). C8051F96x devices also sup-
port an ultra low power internal LFO that reduces sleep mode current.
The SmaRTClock allows a maximum of 36 hour 32-bit independent time-keeping when used with a
32.768 kHz Watch Crystal. The SmaRTClock provides an Alarm and Missing SmaRTClock events, which
could be used as reset or wakeup sources. See Section “22. Reset Sources” on page 278 and Section
“19. Power Management” on page 257 for details on reset sources and low power mode wake-up sources,
respectively.
XTAL4
XTAL3 RTCOUT
SmaRTClock
LFO
Programmable Load Capacitors
SmaRTClock Oscillator
SmaRTClock State Machine
w/ 3 Independent Alarms
Wake-Up
Interrupt
32-Bit
SmaRTClock
Timer
Internal
Registers
CAPTUREn
RTC0CN
RTC0XCN
RTC0XCF
RTC0CF
ALARMnBn
Interface
Registers
RTC0KEY
RTC0ADR
RTC0DAT
Power/
Clock
Mgmt
Figure 24.1. SmaRTClock Block Diagram
Rev. 1.0
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