ATMEGA644P-A15MZ Atmel, ATMEGA644P-A15MZ Datasheet - Page 215

• Manufacturer Part Number: ATMEGA644P-A15MZ
• Description: MCU AVR 64KB FLASH 16MHZ 44QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644P-A15MZ

• Package / Case: 44-VQFN Exposed Pad
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Speed: 16MHz
• Number Of I /o: 32
• Eeprom Size: 2K x 8
• Core Processor: AVR
• Program Memory Type: FLASH
• Ram Size: 4K x 8
• Program Memory Size: 64KB (64K x 8)
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Connectivity: I²C, SPI, UART/USART
• Core Size: 8-Bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

19.5
7674F–AVR–09/09
Overview of the TWI Module
Note that arbitration is not allowed between:
• A REPEATED START condition and a data bit.
• A STOP condition and a data bit.
• A REPEATED START and a STOP condition.
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.
Figure 19-9. Overview of the TWI Module
Slew-rate
Address Match Unit
Arbitration detection
Control
START / STOP
Address Comparator
Address Register
Control
SCL
(TWAR)
Spike
Filter
Bus Interface Unit
Spike Suppression
Address/Data Shift
Register (TWDR)
Slew-rate
Control
SDA
Status Register
ATmega164P/324P/644P
Ack
Spike
Filter
(TWSR)
State Machine and
Control Unit
Status control
Bit Rate Generator
Control Register
Bit Rate Register
Figure
(TWCR)
Prescaler
(TWBR)
19-9. All registers
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