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6437E–ATARM–23-Apr-13
SAM9M11
31. Two-wire Interface (TWI)
31.1
Description
The Atmel Two-wire Interface (TWI) interconnects components on a unique two-wire bus, made
up of one clock line and one data line with speeds of up to 400 Kbits per second, based on a
byte-oriented transfer format. It can be used with any Atmel Two-wire Interface bus Serial
EEPROM and IC compatible device such as Real Time Clock (RTC), Dot Matrix/Graphic LCD
Controllers and Temperature Sensor, to name but a few. The TWI is programmable as a master
or a slave with sequential or single-byte access. Multiple master capability is supported. 20
Arbitration of the bus is performed internally and puts the TWI in slave mode automatically if the
bus arbitration is lost.
A configurable baud rate generator permits the output data rate to be adapted to a wide range of
core clock frequencies.
Below,
Table 31-1 lists the compatibility level of the Atmel Two-wire Interface in Master Mode and
a full I2C compatible device.
Note:
1. START + b000000001 + Ack + Sr
31.2
Embedded Characteristics
Compatibility with standard two-wire serial memory
One, two or three bytes for slave address
Sequential read/write operations
Supports either master or slave modes
Compatible with Standard Two-wire Serial Memories
Master, Multi-master and Slave Mode Operation
Bit Rate: Up to 400 Kbits
General Call Supported in Slave mode
Table 31-1.
Atmel TWI compatibility with I2C Standard
I2C Standard
Atmel TWI
Standard Mode Speed (100 KHz)
Supported
Fast Mode Speed (400 KHz)
Supported
7 or 10 bits Slave Addressing
Supported
Not Supported
Repeated Start (Sr) Condition
Supported
ACK and NACK Management
Supported
Slope control and input filtering (Fast mode)
Not Supported
Clock stretching
Supported
Multi Master Capability
Supported