ATmega128A Atmel Corporation, ATmega128A Datasheet - Page 175

• Manufacturer Part Number: ATmega128A
• Manufacturer: Atmel Corporation

Specifications of ATmega128A

• Flash (kbytes): 128 Kbytes
• Pin Count: 64
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 53
• Ext Interrupts: 8
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Uart: 2
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 4
• Eeprom (bytes): 4096
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 4
• Output Compare Channels: 8
• Input Capture Channels: 2
• Pwm Channels: 7
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

20.2.1
8151H–AVR–02/11
AVR USART vs. AVR UART – Compatibility
Figure 20-1. USART Block Diagram
Note:
The dashed boxes in the block diagram separate the three main parts of the USART (listed from
the top): Clock Generator, Transmitter, and Receiver. Control registers are shared by all units.
The clock generation logic consists of synchronization logic for external clock input used by syn-
chronous slave operation, and the baud rate generator. The XCK (Transfer Clock) pin is only
used by Synchronous Transfer mode. The Transmitter consists of a single write buffer, a serial
Shift Register, parity generator and control logic for handling different serial frame formats. The
write buffer allows a continuous transfer of data without any delay between frames. The
Receiver is the most complex part of the USART module due to its clock and data recovery
units. The recovery units are used for asynchronous data reception. In addition to the recovery
units, the receiver includes a parity checker, control logic, a Shift Register and a two level
receive buffer (UDR). The receiver supports the same frame formats as the Transmitter, and can
detect frame error, data overrun and parity errors.
The USART is fully compatible with the AVR UART regarding:
• Bit locations inside all USART registers
• Baud Rate Generation
Refer to
pin placement.
Figure 1-1 on page
UCSRA
TRANSMIT SHIFT REGISTER
RECEIVE SHIFT REGISTER
BAUD RATE GENERATOR
UDR (Transmit)
2,
UDR (Receive)
UBRR[H:L]
Table 12-11 on page
UCSRB
GENERATOR
SYNC LOGIC
RECOVERY
RECOVERY
CHECKER
PARITY
CLOCK
PARITY
DATA
78, and
OSC
Table 12-14 on page 81
Clock Generator
CONTROL
CONTROL
CONTROL
CONTROL
CONTROL
Transmitter
ATmega128A
PIN
PIN
PIN
RX
TX
Receiver
UCSRC
XCK
RxD
TxD
for USART
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