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DS1302 Series Datasheet

DS1302

Trickle-Charge Timekeeping Chip

The DS1302 real-time timing chip includes a real-time clock/calendar and 31 bytes of static RAM. It communicates with the microprocessor through a simple serial interface. The real-time clock/calendar provides second, minute, hour, day, day, month and year information. For months with fewer than 31 days, the month-end date is automatically adjusted, including corrections for leap years. The clock runs in a 24-hour or 12-hour format and has an AM/PM indicator.

DS1302 Data sheet.pdf

DS1302 Pin Configuration and Function

Pin Number	Pin Name	Description
1	Vcc2	Primary Power-Supply Pin in Dual Supply Configuration.Vcc is connected to abackup source to maintain the time and date in the absence of primary power.TheDS1302 operates from the larger of Vcc1 or Vcc2.When Vcc2 is greater than Vcc1+0.2V,Vcco powers the DS1302.When Vcc2 is less than Vcc1,Vcc1 powers the DS1302.
2	X1	Connections for Standard 32.768kHz Quartz Crystal.The internal oscillator isdesigned for operation with a crystal having a specified load capacitance of 6pF.For more information on crystal selection and crystal layout considerations, refer toApplication Note 58: Crystal Considerations for Dallas Real-Time Clocks.The DS1302 can also be driven by an external 32.768kHz oscillator. In this configuration, the X1 pin is connected to the external oscillator signal and the X2 pinis floated.
3	X2
4	GND	Ground
5	CE	Input.CE signal must be asserted high during a read or a write.This pin has aninternal 40k2 (typ) pulldown resistor to ground. Note: Previous data sheet revisionsreferred to CE as RST.The functionality of the pin has not changed.
6	I/O	Input/Push-Pull Output.The l/O pin is the bidirectional data pin for the 3-wireinterface.This pin has an internal 40kQ (typ) pulldown resistor to ground.
7	SCLK	Input.SCLK is used to synchronize data movement on the serial interface.This pinhas an internal 40kQ (typ) pulldown resistor to ground.
8	Vcc1	Low-Power Operation in Single Supply and Battery-Operated Systems and Low-Power Battery Backup.In systems using the trickle charger, the rechargeableenergy source is connected to this pin.UL recognized to ensure against reversecharging current when used with a lithium battery.