ATmega1281R231 Atmel Corporation, ATmega1281R231 Datasheet - Page 227

• Manufacturer Part Number: ATmega1281R231
• Manufacturer: Atmel Corporation

Specifications of ATmega1281R231

• Flash (kbytes): 128 Kbytes
• Max. Operating Frequency: 16 MHz
• Max I/o Pins: 54
• Spi: 3
• Twi (i2c): 1
• Uart: 2
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Crypto Engine: AES
• Sram (kbytes): 8
• Eeprom (bytes): 4096
• Operating Voltage (vcc): 1.8 to 3.6
• Timers: 6
• Frequency Band: 2.4 GHz
• Max Data Rate (mb/s): 2
• Antenna Diversity: Yes
• External Pa Control: Yes
• Power Output (dbm): 3
• Receiver Sensitivity (dbm): -101
• Receive Current Consumption (ma): 13.2
• Transmit Current Consumption (ma): 14.4
• Link Budget (dbm): 104

22.9.5
22.10 Examples of Baud Rate Setting
Table 22-9.
2549N–AVR–05/11
14.4K
19.2K
28.8K
38.4K
Baud
(bps)
Rate
2400
4800
9600
UBRRnL and UBRRnH – USART Baud Rate Registers
UBRR
25
12
6
3
2
1
1
Examples of UBRRn Settings for Commonly Used Oscillator Frequencies
U2Xn = 0
f
-18.6%
-7.0%
osc
Error
0.2%
0.2%
8.5%
8.5%
8.5%
= 1.0000MHz
• Bit 15:12 – Reserved Bits
These bits are reserved for future use. For compatibility with future devices, these bit must be
written to zero when UBRRH is written.
• Bit 11:0 – UBRR11:0: USART Baud Rate Register
This is a 12-bit register which contains the USART baud rate. The UBRRH contains the four
most significant bits, and the UBRRL contains the eight least significant bits of the USART baud
rate. Ongoing transmissions by the Transmitter and Receiver will be corrupted if the baud rate is
changed. Writing UBRRL will trigger an immediate update of the baud rate prescaler.
For standard crystal and resonator frequencies, the most commonly used baud rates for asyn-
chronous operation can be generated by using the UBRR settings in
on page
get baud rate, are bold in the table. Higher error ratings are acceptable, but the Receiver will
have less noise resistance when the error ratings are high, especially for large serial frames (see
“Asynchronous Operational Range” on page
lowing equation:
Bit
Read/Write
Initial Value
UBRR
51
25
12
8
6
3
2
U2Xn = 1
231. UBRR values which yield an actual baud rate differing less than 0.5% from the tar-
-3.5%
-7.0%
Error
0.2%
0.2%
0.2%
8.5%
8.5%
R/W
15
R
–
7
0
0
UBRR
47
23
11
7
5
3
2
R/W
U2Xn = 0
14
R
–
6
0
0
Error[%]
f
ATmega640/1280/1281/2560/2561
osc
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
R/W
13
=
R
= 1.8432MHz
–
5
0
0
⎛
⎝
BaudRate
------------------------------------------------------- - 1
UBRR
95
47
23
15
11
BaudRate
R/W
7
5
12
R
–
4
0
0
U2Xn = 1
220). The error values are calculated using the fol-
UBRR[7:0]
Closest Match
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
R/W
R/W
11
3
0
0
–
UBRR
⎞
⎠
R/W
R/W
51
25
12
10
•
2
0
0
8
6
3
2
UBRR[11:8]
100%
U2Xn = 0
f
Table 22-9
-3.5%
-7.0%
osc
Error
0.2%
0.2%
0.2%
8.5%
8.5%
R/W
R/W
9
1
0
0
= 2.0000MHz
UBRR
R/W
R/W
103
8
0
0
0
51
25
16
12
to
8
6
U2Xn = 1
Table 22-12
UBRRHn
UBRRLn
-3.5%
-7.0%
Error
0.2%
0.2%
0.2%
2.1%
0.2%
227