The PCF8563 is a CMOS1 Real-Time Clock (RTC) and calendar optimized for low power

consumption. A programmable clock output, interrupt output, and voltage-low detector are

also provided. All addresses and data are transferred serially via a two-line bidirectional

I2C-bus. Maximum bus speed is 400 kbit/s. The register address is incremented

automatically after each written or read data byte.