C8051F9xx devices include an ultra low power 32-bit SmaRTClock Peripheral (Real Time Clock) with alarm. The SmaRTClock has a dedicated 32kHz 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 programmable to sixteen discrete levels, allowing compatibility with a wide range of crystals. The SmaRTClock can operate directly from a 0.9 to 3.6V battery voltage and remains operational even when the device goes into its lowest power sleep mode. On C8051F912/F902 devices, 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. C8051F912/F902 devices also support an ultra low power internal LFO that reduces sleep mode current.