ATMEGA644A-AUR Atmel, ATMEGA644A-AUR Datasheet - Page 236
ATMEGA644A-AUR
Manufacturer Part Number
ATMEGA644A-AUR
Description
IC MCU AVR 64K FLASH 44TQFP
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644A-AUR
Core Processor
AVR
Core Size
8-Bit
Speed
20MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
32
Program Memory Size
64KB (32K x 16)
Program Memory Type
FLASH
Eeprom Size
2K x 8
Ram Size
4K x 8
Voltage - Supply (vcc/vdd)
1.8 V ~ 5.5 V
Data Converters
A/D 8x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
44-TQFP, 44-VQFP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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20.9.5
20.9.6
8272A–AVR–01/10
TWAR – TWI (Slave) Address Register
TWAMR – TWI (Slave) Address Mask Register
of a lost bus arbitration, no data is lost in the transition from Master to Slave. Handling of the
ACK bit is controlled automatically by the TWI logic, the CPU cannot access the ACK bit directly.
• Bits 7:0 – TWD: TWI Data Register
These eight bits constitute the next data byte to be transmitted, or the latest data byte received
on the 2-wire Serial Bus.
The TWAR should be loaded with the 7-bit Slave address (in the seven most significant bits of
TWAR) to which the TWI will respond when programmed as a Slave Transmitter or Receiver,
and not needed in the Master modes. In multimaster systems, TWAR must be set in masters
which can be addressed as Slaves by other Masters.
The LSB of TWAR is used to enable recognition of the general call address (0x00). There is an
associated address comparator that looks for the slave address (or general call address if
enabled) in the received serial address. If a match is found, an interrupt request is generated.
• Bits 7:1 – TWA: TWI (Slave) Address Register
These seven bits constitute the slave address of the TWI unit.
• Bit 0 – TWGCE: TWI General Call Recognition Enable Bit
If set, this bit enables the recognition of a General Call given over the 2-wire Serial Bus.
• Bits 7:1 – TWAM: TWI Address Mask
The TWAMR can be loaded with a 7-bit Slave Address mask. Each of the bits in TWAMR can
mask (disable) the corresponding address bit in the TWI Address Register (TWAR). If the mask
bit is set to one then the address match logic ignores the compare between the incoming
address bit and the corresponding bit in TWAR.
detail.
164A/164PA/324A/324PA/644A/644PA/1284/1284P
Bit
(0xBA)
Read/Write
Initial Value
Bit
(0xBD)
Read/Write
Initial Value
TWA6
R/W
R/W
7
1
7
0
TWA5
R/W
R/W
6
1
6
0
TWA4
R/W
R/W
5
1
5
0
TWAM[6:0]
TWA3
R/W
R/W
4
1
4
0
Figure 20-22
TWA2
R/W
R/W
3
1
3
0
TWA1
R/W
R/W
shows the address match logic in
2
1
2
0
TWA0
R/W
R/W
1
1
1
0
TWGCE
R/W
R
0
0
0
–
0
TWAMR
TWAR
236
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