ATMEGA8U2-AUR Atmel, ATMEGA8U2-AUR Datasheet - Page 151

• Manufacturer Part Number: ATMEGA8U2-AUR
• Description: MCU AVR 8K FLASH 16MHZ 32TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8U2-AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 22
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-TQFP, 32-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Data Converters: -

Table 18-1.
18.3.2
7799D–AVR–11/10
Operating Mode
Asynchronous Normal mode
(U2Xn = 0)
Asynchronous Double Speed
mode (U2Xn = 1)
Synchronous Master mode
Double Speed Operation (U2Xn)
Equations for Calculating Baud Rate Register Setting
Table 18-1
ing the UBRRn value for each mode of operation using an internally generated clock source.
Note:
Some examples of UBRRn values for some system clock frequencies are found in
page
The transfer rate can be doubled by setting the U2Xn bit in UCSRnA. Setting this bit only has
effect for the asynchronous operation. Set this bit to zero when using synchronous operation.
Setting this bit will reduce the divisor of the baud rate divider from 16 to 8, effectively doubling
the transfer rate for asynchronous communication. Note however that the Receiver will in this
case only use half the number of samples (reduced from 16 to 8) for data sampling and clock
recovery, and therefore a more accurate baud rate setting and system clock are required when
this mode is used. For the Transmitter, there are no downsides.
172.
BAUD
f
UBRRn
OSC
1. The baud rate is defined to be the transfer rate in bit per second (bps)
contains equations for calculating the baud rate (in bits per second) and for calculat-
Equation for Calculating Baud Rate
BAUD
BAUD
BAUD
Baud rate (in bits per second, bps)
System Oscillator clock frequency
Contents of the UBRRHn and UBRRLn Registers, (0-4095)
=
=
=
----------------------------------------- -
16 UBRRn
-------------------------------------- -
8 UBRRn
-------------------------------------- -
2 UBRRn
(
(
(
f
f
f
OSC
OSC
OSC
+
+
+
1
1
1
)
)
)
(1)
ATmega8U2/16U2/32U2
Equation for Calculating UBRR Value
UBRRn
UBRRn
UBRRn
=
=
=
----------------------- - 1
16BAUD
------------------- - 1
8BAUD
------------------- - 1
2BAUD
f
f
f
OSC
OSC
OSC
Table 18-9 on
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–
–
151