atmega161-4pi ATMEL Corporation, atmega161-4pi Datasheet - Page 69

• Manufacturer Part Number: atmega161-4pi
• Description: 8-bit Microcontroller With 16k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

UARTs
Data Transmission
1228D–AVR–02/07
The ATmega161 features two full-duplex (separate Receive and Transmit Registers)
Universal Asynchronous Receiver and Transmitters (UARTs). The main features are:
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A block schematic of the UART Transmitter is shown in Figure 44. The two UARTs are
identical and the functionality is described in general for the two UARTs.
Figure 44. UART Transmitter
Data transmission is initiated by writing the data to be transmitted to the UART I/O Data
Register, UDRn. Data is transferred from UDRn to the Transmit Shift Register when:
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XTAL
Baud Rate Generator Generates any Baud Rate
High Baud Rates at low XTAL Frequencies
8 or 9 Bits Data
Noise Filtering
Overrun Detection
Framing Error Detection
False Start Bit Detection
Three Separate Interrupts on TX Complete, TX Data Register Empty, and RX Complete
Multi-processor Communication Mode
Double-speed UART Mode
A new character has been written to UDRn after the stop bit from the previous
character has been shifted out. The Shift Register is loaded immediately.
CONTROL LOGIC
GENERATOR
n = 0,1
BAUD RATE
STORE UDRn
SHIFT ENABLE
BAUD x 16
IDLE
UART CONTROL AND
STATUS REGISTER
/16
DATA BUS
BAUD
(UCSRnB)
DATA BUS
REGISTER (UDRn)
SHIFT REGISTER
UART I/O DATA
10(11)-BIT TX
UART CONTROL AND
TXCn
STATUS REGISTER
IRQ
(UCSRnA)
UDREn
ATmega161(L)
IRQ
TXDn
PIN CONTROL
LOGIC
PD1/
PB3
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