DS1305EN datasheet(3/22 Pages) DALLAS

3 / 22 page

DS1305

3 of 22

DS1305 BLOCK DIAGRAM Figure 1

SIGNAL DESCRIPTIONS

VCC1 - DC power is provided to the device on this pin. VCC1 is the primary power supply.

VCC2 - This is the secondary power supply pin. In systems using the trickle charger, the rechargeable

energy source is connected to this pin.

VBAT - Battery input for any standard 3-volt lithium cell or other energy source.

VCCIF (Interface Logic Power Supply Input) - The VCCIF pin allows the DS1305 to drive SDO and PF

out-put pins to a level that is compatible with the interface logic, thus allowing an easy interface to 3-volt

logic in mixed supply systems. This pin is physically connected to the source connection of the p-channel

transistors in the output buffers of the SDO and PF pins.

SERMODE (Serial Interface Mode Input) - The SERMODE pin offers the flexibility to choose

between two serial interface modes.

When connected to GND, standard 3-wire communication is

selected. When connected to VCC, Motorola SPI communication is selected.

SCLK (Serial Clock Input) - SCLK is used to synchronize data movement on the serial interface for

either the SPI or 3-wire interface.

SDI (Serial Data Input) - When SPI communication is selected, the SDI pin is the serial data input for

the SPI bus. When 3-wire communication is selected, this pin must be tied to the SDO pin (the SDI and

SDO pins function as a single I/O pin when tied together).

SDO (Serial Data Output) - When SPI communication is selected, the SDO pin is the serial data output

for the SPI bus. When 3-wire communication is selected, this pin must be tied to the SDI pin (the SDI

and SDO pins function as a single I/O pin when tied together).

DS1305EN Datasheet(PDF) 3 Page - Dallas Semiconductor