Datasheet

DS1306
3 of 22
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
clock continue to run regardless of the level of V
CC
(as long as a power
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
3-wire communication is selected. When connected to V
CC
, SPI
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
single I/O pin when tied together). V
CCIF
provides the logic-high level.
17 14 V
CCIF
Interface Logic Power-Supply Input. The V
CCIF
pin allows the DS1306 to
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
signal is always present. V
CCIF
provides the logic-high level.
20 16 V
CC1
Primary Power Supply. DC power is provided to the device on this pin.
V
CC1
is the primary power supply.
4, 6, 13,
19
— N.C.
No Connection