DS1305
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).
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DALLAS [ DALLAS SEMICONDUCTOR ]
