DS1306

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ADDRESS AND DATA BYTES

Address and data bytes are shifted MSB first into the serial data input (SDI) and out of the serial data

output (SDO). Any transfer requires the address of the byte to specify a write or read to either a RTC or

RAM location, followed by 1 or more bytes of data. Data is transferred out of the SDO for a read

operation and into the SDI for a write operation (see figures 7 and 8).

SPI SINGLE-BYTE WRITE Figure 7

SPI SINGLE-BYTE READ Figure 8

* SCLK can be either polarity.

The address byte is always the first byte entered after CE is driven high. The most significant bit (A7) of

this byte determines if a read or write will take place. If A7 is 0, one or more read cycles will occur. If

A7 is 1, one or more write cycles will occur.

Data transfers can occur 1 byte at a time or in multiple-byte burst mode. After CE is driven high an

address is written to the DS1306. After the address, 1 or more data bytes can be written or read. For a

single-byte transfer 1 byte is read or written and then CE is driven low. For a multiple-byte transfer,

however, multiple bytes can be read or written to the DS1306 after the address has been written. Each

read or write cycle causes the RTC register or RAM address to automatically increment. Incrementing

continues until the device is disabled.

When the RTC is selected, the address wraps to 00h after

incrementing to 1Fh (during a read) and wraps to 80h after incrementing to 9Fh (during a write). When

the RAM is selected, the address wraps to 20h after incrementing to 7Fh (during a read) and wraps to

A0h after incrementing to FFh (during a write).