ATMEGA32U4-AU Atmel, ATMEGA32U4-AU Datasheet - Page 193

• Manufacturer Part Number: ATMEGA32U4-AU
• Description: MCU AVR 32K FLASH 16MHZ 44-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA32U4-AU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 26
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 1K x 8
• Ram Size: 2.5K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 12x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Processor Series: ATMEGA32x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 2.5 KB
• Interface Type: SPI/TWI/USART
• Maximum Clock Frequency: 16 MHz
• Number Of Programmable I/os: 26
• Number Of Timers: 5
• 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: 12-ch x 10-bit
• Cpu Family: ATmega
• Device Core: AVR
• Device Core Size: 8b
• Frequency (max): 16MHz
• Total Internal Ram Size: 2.5KB
• # I/os (max): 26
• Number Of Timers - General Purpose: 5
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 44
• Package Type: TQFP
• Controller Family/series: AVR MEGA
• No. Of I/o's: 26
• Eeprom Memory Size: 1KB
• Ram Memory Size: 2.5KB
• Cpu Speed: 16MHz
• Rohs Compliant: Yes
• For Use With: ATSTK524 - KIT STARTER ATMEGA32M1/MEGA32C1ATSTK600 - DEV KIT FOR AVR/AVR32ATAVRDRAGON - KIT DRAGON 32KB FLASH MEM AVRATSTK500 - PROGRAMMER AVR STARTER KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ATMEGA32U4-16AU; ATMEGA32U4-16AU

18.5
18.5.1
7766F–AVR–11/10
Data Transmission – The USART Transmitter
Sending Frames with 5 to 8 Data Bit
The USART Transmitter is enabled by setting the Transmit Enable (TXEN) bit in the UCSRnB
Register. When the Transmitter is enabled, the normal port operation of the TxDn pin is overrid-
den by the USART and given the function as the Transmitter’s serial output. The baud rate,
mode of operation and frame format must be set up once before doing any transmissions. If syn-
chronous operation is used, the clock on the XCKn pin will be overridden and used as
transmission clock.
A data transmission is initiated by loading the transmit buffer with the data to be transmitted. The
CPU can load the transmit buffer by writing to the UDRn I/O location. The buffered data in the
transmit buffer will be moved to the Shift Register when the Shift Register is ready to send a new
frame. The Shift Register is loaded with new data if it is in idle state (no ongoing transmission) or
immediately after the last stop bit of the previous frame is transmitted. When the Shift Register is
loaded with new data, it will transfer one complete frame at the rate given by the Baud Register,
U2Xn bit or by XCKn depending on mode of operation.
The following code examples show a simple USART transmit function based on polling of the
Data Register Empty (UDREn) Flag. When using frames with less than eight bits, the most sig-
nificant bits written to the UDRn are ignored. The USART has to be initialized before the function
can be used. For the assembly code, the data to be sent is assumed to be stored in Register
R16
Note:
The function simply waits for the transmit buffer to be empty by checking the UDREn Flag,
before loading it with new data to be transmitted. If the Data Register Empty interrupt is utilized,
the interrupt routine writes the data into the buffer.
Assembly Code Example
C Code Example
.
USART_Transmit:
void USART_Transmit( unsigned char data )
{
}
; Wait for empty transmit buffer
sbis UCSRnA,UDREn
rjmp USART_Transmit
; Put data (r16) into buffer, sends the data
out
ret
/* Wait for empty transmit buffer */
while ( !( UCSRnA & (1<<UDREn)) )
/* Put data into buffer, sends the data */
UDRn = data;
1. See “Code Examples” on page 8.
UDRn,r16
;
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(1)
ATmega16/32U4
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