The PCF2131 is a CMOS real time clock (RTC) and calendar with an integrated temperature compensated crystal (Xtal) oscillator (TCXO) and a 32.768 kHz quartz crystal optimized for very high accuracy and ultra-low power consumption. The PCF2131 features: * Selectable I²C-bus or SPI-bus interfaces for full flexibility when selecting the associated MCU/MPU * Backup battery input and switch-over circuit, allowing the RTC to keep track of the time, even when the main power supply is removed * Calendar capabilities to keep tracking of the time from years down to 1/100 seconds * Up to 4 timestamp registers, which can be associated to timestamp input in order to register tampering events * Up to 2 interrupt outputs to enable/disable systems to reduce the overall current consumption