ATMEGA128A-MU Atmel, ATMEGA128A-MU Datasheet - Page 179

• Manufacturer Part Number: ATMEGA128A-MU
• Description: MCU 8BIT 128K ISP FLASH 64-QFN
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA128A-MU

• 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): 2.7 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-MLF®, 64-QFN
• Processor Series: ATMEGA128x
• Core: AVR8
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
• Controller Family/series: AVR MEGA
• No. Of I/o's: 53
• Eeprom Memory Size: 4KB
• Ram Memory Size: 4KB
• Cpu Speed: 16MHz
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

20.4
20.4.1
8151H–AVR–02/11
Frame Formats
Parity Bit Calculation
A serial frame is defined to be one character of data bits with synchronization bits (start and stop
bits), and optionally a parity bit for error checking. The USART accepts all 30 combinations of
the following as valid frame formats:
A frame starts with the start bit followed by the least significant data bit. Then the next data bits,
up to a total of nine, are succeeding, ending with the most significant bit. If enabled, the parity bit
is inserted after the data bits, before the stop bits. When a complete frame is transmitted, it can
be directly followed by a new frame, or the communication line can be set to an idle (high) state.
Figure 20-4
optional.
Figure 20-4. Frame Formats
St
(n)
P
Sp
IDLE
The frame format used by the USART is set by the UCSZ2:0, UPM1:0 and USBS bits in UCSRB
and UCSRC. The receiver and transmitter use the same setting. Note that changing the setting
of any of these bits will corrupt all ongoing communication for both the receiver and transmitter.
The USART Character SiZe (UCSZ2:0) bits select the number of data bits in the frame. The
USART Parity mode (UPM1:0) 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 (USBS) bit. The receiver ignores the
second stop bit. An FE (Frame Error) 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:
P
P
odd
even
• 1 start bit
• 5, 6, 7, 8, or 9 data bits
• no, even or odd parity bit
• 1 or 2 stop bits
(IDLE)
illustrates the possible combinations of the frame formats. Bits inside brackets are
Start bit, always low.
Data bits (0 to 8).
Parity bit. Can be odd or even.
Stop bit, always high.
No transfers on the communication line (RxD or TxD). An IDLE line must be high.
Parity bit using even parity
Parity bit using odd parity
St
0
P
P
even
odd
1
=
=
2
d
d
n 1
n 1
–
–
3
⊕
⊕
…
…
4
FRAME
⊕
⊕
[5]
d
d
3
3
⊕
⊕
[6]
d
d
2
2
⊕
⊕
[7]
d
d
1
1
⊕
⊕
[8]
d
d
0
0
⊕
⊕
[P]
0
1
Sp1 [Sp2]
ATmega128A
(St / IDLE)
179