The DS1302 has a built-in battery-backed SRAM that retains data during power failures. Connect a 3V lithium coin cell battery to the VBAT pin to ensure data retention.
The recommended crystal oscillator frequency for the DS1302 is 32.768 kHz, which is a standard frequency for real-time clocks.
The clock frequency of the DS1302 is set by writing to the Clock Halt (CH) bit in the Seconds register. Set CH=0 to enable the oscillator, and CH=1 to disable it.
Yes, the DS1302 is 5V tolerant, but it's recommended to use a level shifter or voltage divider to ensure the input signals are within the recommended voltage range.
The DS1302 has a century bit that allows it to handle years beyond 1999. Set the century bit (bit 7 of the Year register) to 1 for years 2000 and beyond.
DS1302 datasheet
by Maxim Integrated Products
