DS1306

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PIN DESCRIPTION (continued)

PIN

TSSOP

DIP

NAME

FUNCTION

9

7

1Hz

1Hz Output. The 1Hz pin provides a 1Hz square wave output. This output

is active when the 1 Hz bit in the control register is a logic 1. Both

INT0 and

1Hz pins are open-drain outputs. The interrupt, 1Hz signal, and the internal

source is present).

10

8

GND

Ground

11

9

SERMODE

Serial Interface Mode. The SERMODE pin offers the flexibility to choose

between two serial interface modes. When connected to GND, standard

communication is selected.

12

10

CE

Chip Enable. The chip enable signal must be asserted high during a read or

a write for both 3-wire and SPI communication. This pin has an internal 55k

pulldown resistor (typical).

14

11

SCLK

Serial Clock. SCLK is used to synchronize data movement on the serial

interface for either the SPI or 3-wire interface.

15

12

SDI

Serial Data In. 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).

16

13

SDO

Serial Data Out. 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

17

14

drive SDO and 32kHz output pins to a level that is compatible with the

interface logic, thus allowing an easy interface to 3V 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 32kHz pins.

18

15

32kHz

32.768kHz Output. The 32kHz pin provides a 32.768kHz output. This

20

16

Primary Power Supply. DC power is provided to the device on this pin.

4, 6, 13,

19

—

N.C.

No Connection