DS1305

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3-WIRE INTERFACE

The 3-wire interface mode operates similarly to the SPI mode. However, in 3-wire mode there is one I/O

instead of separate data in and data out signals. The 3-wire interface consists of the I/O (SDI and SDO

pins tied together), CE, and SCLK pins. In 3-wire mode, each byte is shifted in LSB first unlike SPI mode

where each byte is shifted in MSB first.

As is the case with the SPI mode, an address byte is written to the device followed by a single data byte

or multiple data bytes. Figure 9 illustrates a read and write cycle. In 3-wire mode, data is input on the

rising edge of SCLK and output on the falling edge of SCLK.

Figure 9. 3-WIRE SINGLE-BYTE TRANSFER

NOTE: IN BURST MODE, CE IS KEPT HIGH AND ADDITIONAL SCLK CYCLES ARE SENT UNTIL THE END OF THE BURST.

*I/O IS SDI AND SDO TIED TOGETHER.

A0 A1 A2

A3 A4

A5 A6

1

CE

SCLK

I/O*

D0

D1

D2

D3

D4 D5 D6 D7

SINGLE-BYTE WRITE

D0

D1

D2

D3

D4

D5

D6

D7

A0

A1

A2

A3

A4

A5 A6 0

I/O*

CE

SCLK

SINGLE-BYTE READ