PCF85053ATK-ARD is used to evaluate the functions and performances of PCF85053A through the use of Arduino Shield connector. PCF85053A is a CMOS real-time clock (RTC) and calendar optimized for low power consumption and automatic switching to battery on primary power loss. Featuring clock output, alert interrupt output and 128-byte battery backed-up SRAM. The PCF85053A includes two I²C buses: the primary I²C bus has the read/write capability on RTC and SRAM registers; the second I²C bus also can read/write most registers with the control bits set by primary I²C master. PCF85053A offers clock output calibration-related registers such as crystal capacitive load (CL) configuration and offset register setting.