ATmega325PA Atmel Corporation, ATmega325PA Datasheet - Page 181

• Manufacturer Part Number: ATmega325PA
• Manufacturer: Atmel Corporation

20.7.2
8285D–AVR–06/11
Receiving Frames with 9 Data Bits
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P
If 9-bit characters are used (UCSZ=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 Sta-
tus 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.
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