The PCF8523 is a CMOS Real-Time Clock (RTC) and calendar optimized for low power consumption. Data is transferred serially via the I²C-bus with a maximum data rate of 1000 kbit/s. Alarm and timer functions are available with the possibility to generate a wake-up signal on an interrupt pin. An offset register allows fine-tuning of the clock. The PCF8523 has a backup battery switch-over circuit, which detects power failures and automatically switches to the battery supply when a power failure occurs.
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## Features
* Provides year, month, day, weekday, hours, minutes, and seconds based on a 32.768 kHz quartz crystal
* Resolution: seconds to years
* Clock operating voltage: 1.0 V to 5.5 V
* Low backup current: typical 150 nA at VDD = 3.0 V and Tamb = 25 °C
* 2 line bidirectional 1 MHz Fast-mode Plus (Fm+) I²C interface, read D1h, write D0h
* Battery backup input pin and switch-over circuit
* Freely programmable timer and alarm with interrupt capability
* Selectable integrated oscillator load capacitors for CL = 7 pF or CL = 12.5 pF
* Internal Power-On Reset (POR)
* Open-drain interrupt or clock output pins
* Programmable offset register for frequency adjustment
