ATMEGA640V-8CU Atmel, ATMEGA640V-8CU Datasheet - Page 223
![IC MCU AVR 64K FLASH 100-CBGA](/photos/6/89/68968/313-100-cbga_sml.jpg)
ATMEGA640V-8CU
Manufacturer Part Number
ATMEGA640V-8CU
Description
IC MCU AVR 64K FLASH 100-CBGA
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA640V-8CU
Core Processor
AVR
Core Size
8-Bit
Speed
8MHz
Connectivity
EBI/EMI, I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
86
Program Memory Size
64KB (32K x 16)
Program Memory Type
FLASH
Eeprom Size
4K x 8
Ram Size
8K x 8
Voltage - Supply (vcc/vdd)
1.8 V ~ 5.5 V
Data Converters
A/D 16x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
100-TFBGA
Processor Series
ATMEGA64x
Core
AVR8
Data Bus Width
8 bit
Data Ram Size
8 KB
Interface Type
2-Wire, SPI, USART
Maximum Clock Frequency
8 MHz
Number Of Programmable I/os
86
Number Of Timers
6
Maximum Operating Temperature
+ 85 C
Mounting Style
SMD/SMT
Minimum Operating Temperature
- 40 C
On-chip Adc
10 bit, 16 Channel
For Use With
ATSTK600-TQFP100 - STK600 SOCKET/ADAPTER 100-TQFP770-1007 - ISP 4PORT ATMEL AVR MCU SPI/JTAGATAVRISP2 - PROGRAMMER AVR IN SYSTEMATSTK503 - STARTER KIT AVR EXP MODULE 100P
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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21.9.2
2549M–AVR–09/10
UCSRnA – USART Control and Status Register A
The USART Transmit Data Buffer Register and USART Receive Data Buffer Registers share the
same I/O address referred to as USART Data Register or UDRn. The Transmit Data Buffer Reg-
ister (TXB) will be the destination for data written to the UDRn Register location. Reading the
UDRn Register location will return the contents of the Receive Data Buffer Register (RXB).
For 5-, 6-, or 7-bit characters the upper unused bits will be ignored by the Transmitter and set to
zero by the Receiver.
The transmit buffer can only be written when the UDREn Flag in the UCSRnA Register is set.
Data written to UDRn when the UDREn Flag is not set, will be ignored by the USART Transmit-
ter. When data is written to the transmit buffer, and the Transmitter is enabled, the Transmitter
will load the data into the Transmit Shift Register when the Shift Register is empty. Then the
data will be serially transmitted on the TxDn pin.
The receive buffer consists of a two level FIFO. The FIFO will change its state whenever the
receive buffer is accessed. Due to this behavior of the receive buffer, do not use Read-Modify-
Write instructions (SBI and CBI) on this location. Be careful when using bit test instructions
(SBIC and SBIS), since these also will change the state of the FIFO.
• Bit 7 – RXCn: USART Receive Complete
This flag bit is set when there are unread data in the receive buffer and cleared when the receive
buffer is empty (that is, does not contain any unread data). If the Receiver is disabled, the
receive buffer will be flushed and consequently the RXCn bit will become zero. The RXCn Flag
can be used to generate a Receive Complete interrupt (see description of the RXCIEn bit).
• Bit 6 – TXCn: USART Transmit Complete
This flag bit is set when the entire frame in the Transmit Shift Register has been shifted out and
there are no new data currently present in the transmit buffer (UDRn). The TXCn Flag bit is auto-
matically cleared when a transmit complete interrupt is executed, or it can be cleared by writing
a one to its bit location. The TXCn Flag can generate a Transmit Complete interrupt (see
description of the TXCIEn bit).
• Bit 5 – UDREn: USART Data Register Empty
The UDREn Flag indicates if the transmit buffer (UDRn) is ready to receive new data. If UDREn
is one, the buffer is empty, and therefore ready to be written. The UDREn Flag can generate a
Data Register Empty interrupt (see description of the UDRIEn bit).
UDREn is set after a reset to indicate that the Transmitter is ready.
• Bit 4 – FEn: Frame Error
This bit is set if the next character in the receive buffer had a Frame Error when received, that is,
when the first stop bit of the next character in the receive buffer is zero. This bit is valid until the
receive buffer (UDRn) is read. The FEn bit is zero when the stop bit of received data is one.
Always set this bit to zero when writing to UCSRnA.
Bit
Read/Write
Initial Value
RXCn
R
7
0
TXCn
R/W
6
0
ATmega640/1280/1281/2560/2561
UDREn
R
5
1
FEn
R
4
0
DORn
R
3
0
UPEn
R
2
0
U2Xn
R/W
1
0
MPCMn
R/W
0
0
UCSRnA
223
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