Atmel Xplained Evaluation Board AT32UC3A3-XPLD AT32UC3A3-XPLD 数据表

32072H–AVR32–10/2012

The data put on the TWD line must be 8 bits long. Data is transferred MSB first; each byte must
be followed by an acknowledgement. The number of bytes per transfer is unlimited (see 

).

Each transfer begins with a START condition and terminates with a STOP condition (see 

).

• A high-to-low transition on the TWD line while TWCK is high defines the START condition.

• A low-to-high transition on the TWD line while TWCK is high defines a STOP condition.

Figure 23-3.  START and STOP Conditions 

Figure 23-4. Transfer Format

The TWIM has two modes of operation:

• Master transmitter mode

• Master receiver mode

The master is the device which starts and stops a transfer and generates the TWCK clock.
These modes are described in the following chapters.

TWD

TWCK

Start

Stop

TWD

TWCK

Start

Address

R/W

Ack

Data

Ack

Data

Ack

Stop