ATMEGA8A-PU Atmel, ATMEGA8A-PU Datasheet - Page 172

• Manufacturer Part Number: ATMEGA8A-PU
• Description: MCU AVR 8K FLASH 16MHZ 28-PDIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8A-PU

• 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: 23
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 6x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 28-DIP (0.300", 7.62mm)
• Processor Series: ATMEGA8x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 1 KB
• Interface Type: SPI, TWI, USART
• Maximum Clock Frequency: 16 MHz
• Number Of Programmable I/os: 23
• Number Of Timers: 3
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 6 Channel
• Package: 28PDIP
• Device Core: AVR
• Family Name: ATmega
• Maximum Speed: 16 MHz
• Operating Supply Voltage: 3.3|5 V
• Controller Family/series: AVR MEGA
• No. Of I/o's: 23
• Eeprom Memory Size: 512Byte
• Ram Memory Size: 1KB
• Cpu Speed: 16MHz
• Rohs Compliant: Yes
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATSTK500 - PROGRAMMER AVR STARTER KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8159D–AVR–02/11
Figure 20-8. SCL Synchronization Between Multiple Masters
Arbitration is carried out by all masters continuously monitoring the SDA line after outputting
data. If the value read from the SDA line does not match the value the Master had output, it has
lost the arbitration. Note that a Master can only lose arbitration when it outputs a high SDA value
while another Master outputs a low value. The losing Master should immediately go to Slave
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 20-9. Arbitration Between Two Masters
Note that arbitration is not allowed between:
SCL from
SCL from
Master A
Master B
SCL Bus
Synchronized
Line
SCL Line
SDA from
SDA from
Master A
Master B
SDA Line
START
TA
Counting Low Period
low
Masters Start
TB
low
Arbitration, SDA
Master A Loses
TA
Counting High Period
high
Masters Start
TB
high
A
ATmega8A
SDA
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