AT91RM9200-QI-002 Atmel, AT91RM9200-QI-002 Datasheet - Page 397

• Manufacturer Part Number: AT91RM9200-QI-002
• Description: IC ARM9 MCU 208 PQFP
• Manufacturer: Atmel
• Series: AT91SAMr

Specifications of AT91RM9200-QI-002

• Core Processor: ARM9
• Core Size: 16/32-Bit
• Speed: 180MHz
• Connectivity: EBI/EMI, Ethernet, I²C, MMC, SPI, SSC, UART/USART, USB
• Peripherals: POR
• Number Of I /o: 122
• Program Memory Size: 128KB (128K x 8)
• Program Memory Type: ROM
• Ram Size: 48K x 8
• Voltage - Supply (vcc/vdd): 1.65 V ~ 1.95 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 208-MQFP, 208-PQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Data Converters: -

29.5.2
29.5.3
1768I–ATARM–09-Jul-09
Modes of Operation
Transmitting Data
Figure 29-3.
Figure 29-4. Transfer Format
The TWI has two modes of operations:
The TWI Control Register (TWI_CR) allows configuration of the interface in Master Mode. In this
mode, it generates the clock according to the value programmed in the Clock Waveform Gener-
ator Register (TWI_CWGR). This register defines the TWCK signal completely, enabling the
interface to be adapted to a wide range of clocks.
After the master initiates a Start condition, it sends a 7-bit slave address, configured in the Mas-
ter Mode register (DADR in TWI_MMR), to notify the slave device. The bit following the slave
address indicates the transfer direction (write or read). If this bit is 0, it indicates a write operation
(transmit operation). If the bit is 1, it indicates a request for data read (receive operation).
The TWI transfers require the slave to acknowledge each received byte. During the acknowl-
edge clock pulse, the master releases the data line (HIGH), enabling the slave to pull it down in
order to generate the acknowledge. The master polls the data line during this clock pulse and
sets the NAK bit in the status register if the slave does not acknowledge the byte. As with the
other status bits, an interrupt can be generated if enabled in the interrupt enable register
(TWI_IER). After writing in the transmit-holding register (TWI_THR), setting the START bit in the
control register starts the transmission. The data is shifted in the internal shifter and when an
acknowledge is detected, the TXRDY bit is set until a new write in the TWI_THR (see
6 on page
The read sequence begins by setting the START bit. When the RXRDY bit is set in the status
register, a character has been received in the receive-holding register (TWI_RHR). The RXRDY
bit is reset when reading the TWI_RHR.
The TWI interface performs various transfer formats (7-bit slave address, 10-bit slave address).
The three internal address bytes are configurable through the Master Mode register
(TWI_MMR). If the slave device supports only a 7-bit address, the IADRSZ must be set to 0. For
• Master transmitter mode
• Master receiver mode
398). The master generates a stop condition to end the transfer.
TWD
TWCK
START and STOP Conditions
Start
Address
TWCK
TWD
R/W
Start
Ack
Data
Ack
Data
Stop
AT91RM9200
Ack
Stop
Figure 29-
397