ATMEGA16U4-AU Atmel, ATMEGA16U4-AU Datasheet - Page 194

• Manufacturer Part Number: ATMEGA16U4-AU
• Description: MCU AVR 16K FLASH USB 44TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA16U4-AU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 26
• Program Memory Size: 16KB (8K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 1.25K 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: ATMEGA16x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 1.25 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: 10 bit, 12 Channel
• For Use With: ATSTK600 - DEV KIT FOR AVR/AVR32ATAVRDRAGON - KIT DRAGON 32KB FLASH MEM AVRATSTK500 - PROGRAMMER AVR STARTER KIT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

18.5.2
18.5.3
7766F–AVR–11/10
Sending Frames with 9 Data Bit
Transmitter Flags and Interrupts
If 9-bit characters are used (UCSZn = 7), the ninth bit must be written to the TXB8 bit in
UCSRnB before the low byte of the character is written to UDRn. The following code examples
show a transmit function that handles 9-bit characters. For the assembly code, the data to be
sent is assumed to be stored in registers R17:R16.
Notes:
The ninth bit can be used for indicating an address frame when using multi processor communi-
cation mode or for other protocol handling as for example synchronization.
The USART Transmitter has two flags that indicate its state: USART Data Register Empty
(UDREn) and Transmit Complete (TXCn). Both flags can be used for generating interrupts.
The Data Register Empty (UDREn) Flag indicates whether the transmit buffer is ready to receive
new data. This bit is set when the transmit buffer is empty, and cleared when the transmit buffer
contains data to be transmitted that has not yet been moved into the Shift Register. For compat-
ibility with future devices, always write this bit to zero when writing the UCSRnA Register.
Assembly Code Example
C Code Example
USART_Transmit:
void USART_Transmit( unsigned int data )
{
}
; Wait for empty transmit buffer
sbis UCSRnA,UDREn
rjmp USART_Transmit
; Copy 9th bit from r17 to TXB8
cbi
sbrc r17,0
sbi
; Put LSB data (r16) into buffer, sends the data
out
ret
/* Wait for empty transmit buffer */
while ( !( UCSRnA & (1<<UDREn))) )
/* Copy 9th bit to TXB8 */
UCSRnB &= ~(1<<TXB8);
if ( data & 0x0100 )
/* Put data into buffer, sends the data */
UDRn = data;
1. These transmit functions are written to be general functions. They can be optimized if the con-
2. See “Code Examples” on page 8.
UCSRnB |= (1<<TXB8);
tents of the UCSRnB is static. For example, only the TXB8 bit of the UCSRnB Register is used
after initialization.
UCSRnB,TXB8
UCSRnB,TXB8
UDRn,r16
;
(1)(2)
(1)(2)
ATmega16/32U4
194