ATMEGA48A-MMH Atmel, ATMEGA48A-MMH Datasheet - Page 191
![IC MCU AVR 4K FLASH 28QFN](/photos/12/32/123209/28m1-vqfn_sml.jpg)
ATMEGA48A-MMH
Manufacturer Part Number
ATMEGA48A-MMH
Description
IC MCU AVR 4K FLASH 28QFN
Manufacturer
Atmel
Series
AVR® ATmegar
Specifications of ATMEGA48A-MMH
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
23
Program Memory Size
4KB (2K x 16)
Program Memory Type
FLASH
Eeprom Size
256 x 8
Ram Size
512 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
28-VQFN Exposed Pad, 28-HVQFN, 28-SQFN, 28-DHVQFN
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
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19.7.6
19.7.7
19.8
8271C–AVR–08/10
Asynchronous Data Reception
Disabling the Receiver
Flushing the Receive Buffer
Checker calculates the parity of the data bits in incoming frames and compares the result with
the parity bit from the serial frame. The result of the check is stored in the receive buffer together
with the received data and stop bits. The Parity Error (UPEn) Flag can then be read by software
to check if the frame had a Parity Error.
The UPEn bit is set if the next character that can be read from 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.
In contrast to the Transmitter, disabling of the Receiver will be immediate. Data from ongoing
receptions will therefore be lost. When disabled (i.e., the RXENn is set to zero) the Receiver will
no longer override the normal function of the RxDn port pin. The Receiver buffer FIFO will be
flushed when the Receiver is disabled. Remaining data in the buffer will be lost
The receiver buffer FIFO will be flushed when the Receiver is disabled, i.e., the buffer will be
emptied of its contents. Unread data will be lost. If the buffer has to be flushed during normal
operation, due to for instance an error condition, read the UDRn I/O location until the RXCn Flag
is cleared. The following code example shows how to flush the receive buffer.
Note:
The USART includes a clock recovery and a data recovery unit for handling asynchronous data
reception. The clock recovery logic is used for synchronizing the internally generated baud rate
clock to the incoming asynchronous serial frames at the RxDn pin. The data recovery logic sam-
ples and low pass filters each incoming bit, thereby improving the noise immunity of the
Receiver. The asynchronous reception operational range depends on the accuracy of the inter-
nal baud rate clock, the rate of the incoming frames, and the frame size in number of bits.
ATmega48A/48PA/88A/88PA/168A/168PA/328/328
Assembly Code Example
C Code Example
USART_Flush:
void USART_Flush( void )
{
}
in r16, UCSRnA
sbrs r16, RXCn
ret
in
rjmp USART_Flush
unsigned char dummy;
while ( UCSRnA & (1<<RXCn) ) dummy = UDRn;
1.
See ”About Code Examples” on page 7.
For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI”
instructions must be replaced with instructions that allow access to extended I/O. Typically
“LDS” and “STS” combined with “SBRS”, “SBRC”, “SBR”, and “CBR”.
r16, UDRn
(1)
(1)
191
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