Rainbow Electronics DS1306 - Manual (Page 4)

DS1306
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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). V
CCIF
provides the logic high level.
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).
INT0 (Interrupt 0 Output) – The INT0 pin is an active-low output of the DS1306 that can be used as an
interrupt input to a processor. The INT0 pin can be programmed to be asserted by Alarm 0. The INT0 pin
remains low as long as the status bit causing the interrupt is present and the corresponding interrupt
enable bit is set. The
INT0 pin operates when the DS1306 is powered by V
CC1
, V
CC2
, or V
BAT
. The INT0
pin is an open-drain output and requires an external pullup resistor.
1Hz (1Hz Clock 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).
INT1 (Interrupt 1 Output) – The INT1 pin is an active high output of the DS1306 that can be used as an
interrupt input to a processor. The INT1 pin can be programmed to be asserted by Alarm 1. When an
alarm condition is present, the INT1 pin generates a 62.5ms active-high pulse. The INT1 pin operates
only when the DS1306 is powered by V
CC2
or V
BAT
. When active, the INT1 pin is internally pulled up to
V
CC2
or V
BAT
. When inactive, the INT1 pin is internally pulled low.
32kHz (32.768kHz Clock Output) – The 32kHz pin provides a 32.768kHz output. This signal is always
present. V
CCIF
provides the logic high level.
X1, X2 – Connections for a standard 32.768kHz quartz crystal. The internal oscillator is designed for
operation with a crystal having a specified load capacitance of 6pF. For more information on crystal
selection and crystal layout considerations, refer to Application Note 58, “Crystal Considerations with
Dallas Real-Time Clocks.” The DS1306 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 pin is floated.