ATmega328P datasheet(181/345 Pages) ATMEL

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181

7810A–AVR–11/09

ATmega328P [Preliminary]

19.7.5

Parity Checker

The Parity Checker is active when the high USART Parity mode (UPMn1) bit is set. Type of Par-

ity Check to be performed (odd or even) is selected by the UPMn0 bit. When enabled, the Parity

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.

19.7.6

Disabling the Receiver

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

19.7.7

Flushing the Receive Buffer

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:

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”.

Assembly Code Example

(1)

USART_Flush:

sbis

UCSRnA, RXCn

ret

r16, UDRn

rjmp

USART_Flush

C Code Example(1)

void

USART_Flush( void )

{

unsigned char

dummy;

while

( UCSRnA & (1<<RXCn) ) dummy = UDRn;

}

ATmega328P Datasheet(PDF) 181 Page - ATMEL Corporation

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