ATMEGA128-16AI Atmel, ATMEGA128-16AI Datasheet - Page 198

• Manufacturer Part Number: ATMEGA128-16AI
• Description: IC AVR MCU 128K 16MHZ 64-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA128-16AI

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: EBI/EMI, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TQFP, 64-VQFP
• For Use With: ATSTK501 - ADAPTER KIT FOR 64PIN AVR MCU
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: Q1167170A

Data Transfer and
Frame Format
Transferring Bits
START and STOP
Conditions
198
ATmega128
high. Note that all AVR devices connected to the TWI bus must be powered in order to allow any
bus operation.
The number of devices that can be connected to the bus is only limited by the bus capacitance
limit of 400pF and the 7-bit slave address space. A detailed specification of the electrical charac-
teristics of the TWI is given in
different sets of specifications are presented there, one relevant for bus speeds below 100kHz,
and one valid for bus speeds up to 400kHz.
Each data bit transferred on the TWI bus is accompanied by a pulse on the clock line. The level
of the data line must be stable when the clock line is high. The only exception to this rule is for
generating start and stop conditions.
Figure 87. Data Validity
The master initiates and terminates a data transmission. The transmission is initiated when the
master issues a START condition on the bus, and it is terminated when the master issues a
STOP condition. Between a START and a STOP condition, the bus is considered busy, and no
other master should try to seize control of the bus. A special case occurs when a new START
condition is issued between a START and STOP condition. This is referred to as a REPEATED
START condition, and is used when the master wishes to initiate a new transfer without relin-
quishing control of the bus. After a REPEATED START, the bus is considered busy until the next
STOP. This is identical to the START behavior, and therefore START is used to describe both
START and REPEATED START for the remainder of this datasheet, unless otherwise noted. As
depicted below, START and STOP conditions are signalled by changing the level of the SDA
line when the SCL line is high.
Figure 88. START, REPEATED START and STOP Conditions
SDA
SCL
START
SDA
SCL
“Two-wire Serial Interface Characteristics” on page
Data Stable
STOP START
Data Change
Data Stable
REPEATED START
2467V–AVR–02/11
322. Two
STOP