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11054A–ATARM–27-Jul-11
SAM9X25
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11054A–ATARM–27-Jul-11
SAM9X25
38.7.2
Modes of Operation
The TWI has six modes of operations:
• Master transmitter mode
• Master receiver mode
• Multi-master transmitter mode
• Multi-master receiver mode
• Slave transmitter mode
• Slave receiver mode
These modes are described in the following chapters.
38.8
Master Mode
38.8.1
Definition
The Master is the device that starts a transfer, generates a clock and stops it.
38.8.2
Application Block Diagram
Figure 38-5.
Master Mode Typical Application Block Diagram
38.8.3
Programming Master Mode
The following registers have to be programmed before entering Master mode:
1.
DADR (+ IADR if a 10 bit device is addressed): The device address is used
to access slave devices in read or write mode.
2.
CKDIV + CHDIV + CLDIV: Clock Waveform.
3.
SVDIS: Disable the slave mode.
4.
MSEN: Enable the master mode.
38.8.4
Master Transmitter Mode
After the master initiates a Start condition when writing into the Transmit Holding Register,
TWI_THR, it sends a 7-bit slave address, configured in the Master Mode register (DADR in
Host with
TWI
Interface
TWD
TWCK
Atmel TWI
Serial EEPROM
I²C RTC
I²C LCD
Controller
Slave 1
Slave 2
Slave 3
VDD
I²C Temp.
Sensor
Slave 4
Rp: Pull up value as given by the I²C Standard
Rp
Rp
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