ATMEGA128-16AU Atmel, ATMEGA128-16AU Datasheet - Page 173

• Manufacturer Part Number: ATMEGA128-16AU
• Description: IC AVR MCU 128K 16MHZ 5V 64TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA128-16AU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: EBI/EMI, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 4K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-TQFP, 64-VQFP
• Processor Series: ATMEGA128x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: 2-Wire, JTAG, SPI, USART
• Maximum Clock Frequency: 16 MHz
• Number Of Programmable I/os: 53
• Number Of Timers: 4
• Operating Supply Voltage: 4.5 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 10 bit, 8 Channel
• Controller Family/series: AVR MEGA
• No. Of I/o's: 53
• Eeprom Memory Size: 4096Byte
• Ram Memory Size: 4KB
• Cpu Speed: 16MHz
• Rohs Compliant: Yes
• For Use With: ATSTK600-TQFP64 - STK600 SOCKET/ADAPTER 64-TQFP770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAG770-1005 - ISP 4PORT FOR ATMEL AVR MCU JTAG770-1004 - ISP 4PORT FOR ATMEL AVR MCU SPIATAVRISP2 - PROGRAMMER AVR IN SYSTEMATJTAGICE2 - AVR ON-CHIP D-BUG SYSTEMATSTK501 - ADAPTER KIT FOR 64PIN AVR MCUATSTK500 - PROGRAMMER AVR STARTER KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Internal Clock Generation –
The Baud Rate Generator
Double Speed Operation
(U2X)
2467M–AVR–11/04
Signal description:
Internal clock generation is used for the asynchronous and the synchronous master
modes of operation. The description in this section refers to Figure 80.
The USART Baud Rate Register (UBRR) and the down-counter connected to it function
as a programmable prescaler or baud rate generator. The down-counter, running at sys-
tem clock (fosc), is loaded with the UBRR value each time the counter has counted
down to zero or when the UBRRL Register is written. A clock is generated each time the
counter reaches zero. This clock is the baud rate generator clock output (=
fosc/(UBRR+1)). The transmitter divides the baud rate generator clock output by 2, 8, or
16 depending on mode. The baud rate generator output is used directly by the receiver’s
clock and data recovery units. However, the recovery units use a state machine that
uses 2, 8, or 16 states depending on mode set by the state of the UMSEL, U2X and
DDR_XCK bits.
Table 74 contains equations for calculating the baud rate (in bits per second) and for
calculating the UBRR value for each mode of operation using an internally generated
clock source.
Table 74. Equations for Calculating Baud Rate Register Setting
Note:
Some examples of UBRR values for some system clock frequencies are found in Table
82 (see page 194).
The transfer rate can be doubled by setting the U2X bit in UCSRA. 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
Operating Mode
Asynchronous Normal Mode
(U2X = 0)
Asynchronous Double Speed
Mode (U2X = 1)
Synchronous Master Mode
txclk
rxclk
xcki
xcko
fosc
BAUD Baud rate (in bits per second, bps)
f
UBRR Contents of the UBRRH and UBRRL Registers, (0 - 4095)
OSC
1. The baud rate is defined to be the transfer rate in bit per second (bps).
Transmitter clock. (Internal Signal)
Receiver base clock. (Internal Signal)
Input from XCK pin (internal Signal). Used for synchronous slave operation.
Clock output to XCK pin (Internal Signal). Used for synchronous master
operation.
XTAL pin frequency (System Clock).
System Oscillator clock frequency
BAUD
BAUD
BAUD
Equation for Calculating
Baud Rate
=
=
=
-------------------------------------- -
16 UBRR
---------------------------------- -
8 UBRR
---------------------------------- -
2 UBRR
(
(
(
f
f
f
OSC
OSC
OSC
(1)
+
+
+
1
1
1
)
)
)
Equation for Calculating
UBRR
UBRR
UBRR
ATmega128
UBRR Value
=
=
=
----------------------- - 1
16BAUD
------------------- - 1
8BAUD
------------------- - 1
2BAUD
f
f
f
OSC
OSC
OSC
–
–
–
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