ATMEGA8A-AUR Atmel, ATMEGA8A-AUR Datasheet - Page 161

• Manufacturer Part Number: ATMEGA8A-AUR
• Description: MCU AVR 8KB FLASH 16MHZ 32TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8A-AUR

• 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 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

19.11 Examples of Baud Rate Setting
Table 19-9.
1.
8159D–AVR–02/11
Baud
Rate
(bps)
2400
4800
9600
14.4k
19.2k
28.8k
38.4k
57.6k
76.8k
115.2k
230.4k
250k
Max
(1)
UBRR = 0, Error = 0.0%
UBRR
25
12
6
3
2
1
1
0
–
–
–
–
62.5 kbps
Examples of UBRR Settings for Commonly Used Oscillator Frequencies
U2X = 0
f
-18.6%
osc
-7.0%
Error
0.2%
0.2%
8.5%
8.5%
8.5%
8.5%
–
–
–
–
= 1.0000MHz
• 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
which yield an actual baud rate differing less than 0.5% from the target 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
Range” on page
UBRR
51
25
12
8
6
3
2
1
1
0
–
–
125 kbps
U2X = 1
-18.6%
-3.5%
-7.0%
Error
0.2%
0.2%
0.2%
8.5%
8.5%
8.5%
8.5%
–
–
152). The error values are calculated using the following equation:
UBRR
47
23
11
7
5
3
2
1
0
–
–
1
115.2 kbps
U2X = 0
Error[%]
f
-25.0%
osc
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
–
–
= 1.8432MHz
=
⎛
⎝
BaudRate
------------------------------------------------------- - 1
UBRR
95
47
23
15
11
BaudRate
7
5
3
2
1
0
–
230.4 kbps
U2X = 1
Closest Match
Error
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
–
–
UBRR
⎞
⎠
51
25
12
•
8
6
3
2
1
1
0
–
–
125 kbps
100%
U2X = 0
“Asynchronous Operational
f
-18.6%
-3.5%
-7.0%
osc
Table
Error
0.2%
0.2%
0.2%
8.5%
8.5%
8.5%
8.5%
–
-
= 2.0000MHz
ATmega8A
19-9. UBRR values
UBRR
103
51
25
16
12
8
6
3
2
1
–
0
250 kbps
U2X = 1
-3.5%
-7.0%
Error
0.2%
0.2%
0.2%
2.1%
0.2%
8.5%
8.5%
8.5%
0.0%
–
161