ATMEGA644P-20MQ Atmel, ATMEGA644P-20MQ Datasheet - Page 181
ATMEGA644P-20MQ
Manufacturer Part Number
ATMEGA644P-20MQ
Description
MCU AVR 64K FLASH 20MHZ 44-QFN
Manufacturer
Atmel
Series
AVR® ATmegar
Datasheet
1.ATMEGA164P-20AU.pdf
(439 pages)
Specifications of ATMEGA644P-20MQ
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)
2.7 V ~ 5.5 V
Data Converters
A/D 8x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
44-VQFN Exposed Pad
For Use With
ATSTK600 - DEV KIT FOR AVR/AVR32
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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16.8.2
8011O–AVR–07/10
Receiving Frames with 9 Data Bits
Note:
The function simply waits for data to be present in the receive buffer by checking the RXCn Flag,
before reading the buffer and returning the value.
If 9-bit characters are used (UCSZn=7) the ninth bit must be read from the RXB8n bit in
UCSRnB before reading the low bits from the UDRn. This rule applies to the FEn, DORn and
UPEn Status Flags as well. Read status from UCSRnA, then data from UDRn. Reading the
UDRn I/O location will change the state of the receive buffer FIFO and consequently the TXB8n,
FEn, DORn and UPEn bits, which all are stored in the FIFO, will change.
The following code example shows a simple USART receive function that handles both nine bit
characters and the status bits.
Assembly Code Example
C Code Example
USART_Receive:
unsigned char USART_Receive( void )
{
}
; Wait for data to be received
sbis UCSRnA, RXCn
rjmp USART_Receive
; Get and return received data from buffer
in
ret
/* Wait for data to be received */
while ( !(UCSRnA & (1<<RXCn)) )
/* Get and return received data from buffer */
return UDRn;
1. See “About Code Examples” on page 8.
r16, UDRn
;
(1)
(1)
ATmega164P/324P/644P
181
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