ATMEGA644PV-20AU Atmel, ATMEGA644PV-20AU Datasheet - Page 190
![IC MCU AVR 64K FLASH 44-TQFP](/photos/6/70/67042/313-44-tqfp_sml.jpg)
ATMEGA644PV-20AU
Manufacturer Part Number
ATMEGA644PV-20AU
Description
IC MCU AVR 64K FLASH 44-TQFP
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA644PV-20AU
Core Processor
AVR
Core Size
8-Bit
Speed
20MHz
Connectivity
I²C, SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
32
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)
1.8 V ~ 5.5 V
Data Converters
A/D 8x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
44-TQFP, 44-VQFP
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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16.11.3
8011O–AVR–07/10
UCSRnB – USART Control and Status Register n B
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 3 – DORn: Data OverRun
This bit is set if a Data OverRun condition is detected. A Data OverRun occurs when the receive
buffer is full (two characters), it is a new character waiting in the Receive Shift Register, and a
new start bit is detected. This bit is valid until the receive buffer (UDRn) is read. Always set this
bit to zero when writing to UCSRnA.
• Bit 2 – UPEn: USART Parity Error
This bit is set if the next character in the receive buffer had a Parity Error when received and the
Parity Checking was enabled at that point (UPMn1 = 1). This bit is valid until the receive buffer
(UDRn) is read. Always set this bit to zero when writing to UCSRnA.
• Bit 1 – U2Xn: Double the USART Transmission Speed
This bit only has effect for the asynchronous operation. Write this bit to zero when using syn-
chronous operation.
Writing this bit to one will reduce the divisor of the baud rate divider from 16 to 8 effectively dou-
bling the transfer rate for asynchronous communication.
• Bit 0 – MPCMn: Multi-processor Communication Mode
This bit enables the Multi-processor Communication mode. When the MPCMn bit is written to
one, all the incoming frames received by the USART Receiver that do not contain address infor-
mation will be ignored. The Transmitter is unaffected by the MPCMn setting. For more detailed
information see
• Bit 7 – RXCIEn: RX Complete Interrupt Enable n
Writing this bit to one enables interrupt on the RXCn Flag. A USART Receive Complete interrupt
will be generated only if the RXCIEn bit is written to one, the Global Interrupt Flag in SREG is
written to one and the RXCn bit in UCSRnA is set.
• Bit 6 – TXCIEn: TX Complete Interrupt Enable n
Writing this bit to one enables interrupt on the TXCn Flag. A USART Transmit Complete interrupt
will be generated only if the TXCIEn bit is written to one, the Global Interrupt Flag in SREG is
written to one and the TXCn bit in UCSRnA is set.
Bit
Read/Write
Initial Value
RXCIEn
R/W
”Multi-processor Communication Mode” on page
7
0
TXCIEn
R/W
6
0
UDRIEn
R/W
5
0
RXENn
R/W
4
0
ATmega164P/324P/644P
TXENn
R/W
3
0
UCSZn2
R/W
2
0
187.
RXB8n
R
1
0
TXB8n
R/W
0
0
UCSRnB
190
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