The DS1340Z-33+ is an I²C Real-time Clock (RTC) with trickle charger. The real-time clock (RTC)/calendar that is pin compatible and functionally equivalent to the ST M41T00, including the software clock calibration. The device additionally provides trickle-charge capability on the VBACKUP pin, a lower timekeeping voltage and an oscillator STOP flag. Block access of the register map is identical to the ST device. Two additional registers, which are accessed individually, are required for the trickle charger and flag. The clock/calendar provides seconds, minutes, hours, day, date, month and year information. A built-in power-sense circuit detects power failures and automatically switches to the backup supply. Reads and writes are inhibited while the clock continues to run. The device is programmed serially through an I²C bidirectional bus.