ATMEGA32A-AN Atmel, ATMEGA32A-AN Datasheet - Page 182

• Manufacturer Part Number: ATMEGA32A-AN
• Description: IC MCU AVR 32K FLASH 44TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA32A-AN

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

20.5
8155C–AVR–02/11
Overview of the TWI Module
mode, checking if it is being addressed by the winning master. The SDA line should be left high,
but losing masters are allowed to generate a clock signal until the end of the current data or
address packet. Arbitration will continue until only one master remains, and this may take many
bits. If several masters are trying to address the same slave, arbitration will continue into the
data packet.
Figure 20-8. Arbitration between Two Masters
Note that arbitration is not allowed between:
It is the user software’s responsibility to ensure that these illegal arbitration conditions never
occur. This implies that in multi-master systems, all data transfers must use the same composi-
tion of SLA+R/W and data packets. In other words: All transmissions must contain the same
number of data packets, otherwise the result of the arbitration is undefined.
The TWI module is comprised of several submodules, as shown in
drawn in a thick line are accessible through the AVR data bus.
• A REPEATED START condition and a data bit
• A STOP condition and a data bit
• A REPEATED START and a STOP condition
Synchronized
SCL Line
SDA from
SDA from
Master A
Master B
SDA Line
START
Arbitration, SDA
Master A Loses
Figure
ATmega32A
A
SDA
20-9. All registers
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