ATMEGA64-16AI Atmel, ATMEGA64-16AI Datasheet - Page 176

• Manufacturer Part Number: ATMEGA64-16AI
• Description: IC AVR MCU 64K 16MHZ IND 64-TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA64-16AI

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 53
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K 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
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Parity Bit Calculation
USART
Initialization
2490Q–AVR–06/10
the setting of any of these bits will corrupt all ongoing communication for both the Receiver and
Transmitter.
The USART Character Size (UCSZn2:0) bits select the number of data bits in the frame. The
USART Parity mode (UPMn1:0) bits enable and set the type of parity bit. The selection between
one or two stop bits is done by the USART Stop Bit Select n (USBSn) bit. The receiver ignores
the second stop bit. An FEn (Frame Error n) will therefore only be detected in the cases where
the first stop bit is zero.
The parity bit is calculated by doing an exclusive-or of all the data bits. If odd parity is used, the
result of the exclusive or is inverted. The relation between the parity bit and data bits is as
follows::
If used, the parity bit is located between the last data bit and first stop bit of a serial frame.
The USART has to be initialized before any communication can take place. The initialization pro-
cess normally consists of setting the baud rate, setting frame format and enabling the
Transmitter or the Receiver depending on the usage. For interrupt driven USART operation, the
Global Interrupt Flag should be cleared (and interrupts globally disabled) when doing the
initialization.
Before doing a re-initialization with changed baud rate or frame format, be sure that there are no
ongoing transmissions during the period the registers are changed. The TXCn flag can be used
to check that the Transmitter has completed all transfers, and the RXCn flag can be used to
check that there are no unread data in the receive buffer. Note that the TXCn flag must be
cleared before each transmission (before UDRn is written) if it is used for this purpose.
The following simple USART initialization code examples show one assembly and one C func-
tion that are equal in functionality. The examples assume asynchronous operation using polling
(no interrupts enabled) and a fixed frame format. The baud rate is given as a function parameter.
For the assembly code, the baud rate parameter is assumed to be stored in the r17:r16
registers.
P
P
d
n
even
odd
Parity bit using even parity
Parity bit using odd parity
Data bit n of the character
P
P
even
odd
=
=
d
d
n 1
n 1
–
–
⊕
⊕
…
…
⊕
⊕
d
d
3
3
⊕
⊕
d
d
2
2
⊕
⊕
d
d
1
1
⊕
⊕
d
d
0
0
⊕
⊕
0
1
ATmega64(L)
176