ATMEGA8-16PC Atmel, ATMEGA8-16PC Datasheet - Page 152

• Manufacturer Part Number: ATMEGA8-16PC
• Description: IC AVR MCU 8K 16MHZ COM 28-DIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8-16PC

• 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): 4.5 V ~ 5.5 V
• Data Converters: A/D 6x10b
• Oscillator Type: Internal
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 28-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: ATMEGA816PC

USART Baud Rate
Registers – UBRRL
and UBRRHs
152
ATmega8(L)
• Bit 0 – UCPOL: Clock Polarity
This bit is used for Synchronous mode only. Write this bit to zero when Asynchronous mode is
used. The UCPOL bit sets the relationship between data output change and data input sample,
and the synchronous clock (XCK).
Table 59. UCPOL Bit Settings
The UBRRH Register shares the same I/O location as the UCSRC Register. See the
UBRRH/UCSRC Registers” on page 146
• Bit 15 – URSEL: Register Select
This bit selects between accessing the UBRRH or the UCSRC Register. It is read as zero when
reading UBRRH. The URSEL must be zero when writing the UBRRH.
• Bit 14:12 – 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.
Bit
Read/Write
Initial Value
UCPOL
0
1
Transmitted Data Changed
(Output of TxD Pin)
Rising XCK Edge
Falling XCK Edge
URSEL
R/W
R/W
15
7
0
0
R/W
14
R
–
6
0
0
R/W
13
R
–
5
0
0
R/W
12
R
–
4
0
0
UBRR[7:0]
section which describes how to access this register.
R/W
R/W
11
3
0
0
Received Data Sampled
(Input on RxD Pin)
Falling XCK Edge
Rising XCK Edge
R/W
R/W
10
2
0
0
UBRR[11:8]
R/W
R/W
9
1
0
0
R/W
R/W
8
0
0
0
UBRRH
UBRRL
2486Z–AVR–02/11
“Accessing