DS1306
Four pins are used for the SPI. The four pins are the SDO (Serial Data Out), SDI (Serial Data In), CE
(Chip Enable), and SCLK (Serial Clock). The DS1306 is the slave device in an SPI application, with the
microcontroller being the master.
The SDI and SDO pins are the serial data input and output pins for the DS1306, respectively. The CE
input is used to initiate and terminate a data transfer. The SCLK pin is used to synchronize data
movement between the master (microcontroller) and the slave (DS1306) devices.
The shift clock (SCLK), which is generated by the microcontroller, is active only during address and data
transfer to any device on the SPI bus. The inactive clock polarity is programmable in some
microcontrollers. The DS1306 offers an important feature in that the level of the inactive clock is
determined by sampling SCLK when CE becomes active. Therefore either SCLK polarity can be
accommodated. Input data (SDI) is latched on the internal strobe edge and output data (SDO) is shifted
out on the shift edge (see Table 3 and Figure 6). There is one clock for each bit transferred. Address and
data bits are transferred in groups of eight.
POWER SUPPLY CONFIGURATIONS FOR THE DS1306
Figure 5
Configuration 1: Backup Supply is a Non-Rechargeable Lithium Battery
Configuration 2: Backup Supply is a Rechargeable Battery or Super Capacitor
Configuration 3: Battery Operate Mode
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DALLAS [ DALLAS SEMICONDUCTOR ]
