ATmega1281 Atmel Corporation, ATmega1281 Datasheet - Page 269
ATmega1281
Manufacturer Part Number
ATmega1281
Description
Manufacturer
Atmel Corporation
Specifications of ATmega1281
Flash (kbytes)
128 Kbytes
Pin Count
64
Max. Operating Frequency
16 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
54
Ext Interrupts
17
Usb Speed
No
Usb Interface
No
Spi
3
Twi (i2c)
1
Uart
2
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
8
Adc Resolution (bits)
10
Adc Speed (ksps)
15
Analog Comparators
1
Resistive Touch Screen
No
Temp. Sensor
No
Crypto Engine
No
Sram (kbytes)
8
Eeprom (bytes)
4096
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8 to 5.5
Operating Voltage (vcc)
1.8 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
6
Output Compare Channels
16
Input Capture Channels
2
Pwm Channels
8
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
ATmega1281-8MC
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
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24.9.5
24.9.6
2549N–AVR–05/11
TWAR – TWI (Slave) Address Register
TWAMR – TWI (Slave) Address Mask Register
• 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.
Figure 24-22. TWI Address Match Logic, Block Diagram
Bit
(0xBA)
Read/Write
Initial Value
Bit
(0xBD)
Read/Write
Initial Value
TWAMR0
Address
TWAR0
Bit 0
TWA6
R/W
R/W
7
1
7
0
TWA5
R/W
R/W
6
1
6
0
Address Bit Comparator 6..1
ATmega640/1280/1281/2560/2561
TWA4
R/W
R/W
Address Bit Comparator 0
5
1
5
0
TWAM[6:0]
TWA3
R/W
R/W
4
1
4
0
Figure 24-22
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
Address
R
Match
0
0
0
–
0
TWAMR
TWAR
269
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