User guide

187
ATmega162/V
2513E–AVR–09/03
• Bit 5 – UDRIE: USART Data Register Empty Interrupt Enable
Writing this bit to one enables interrupt on the UDRE Flag. A Data Register Empty inter-
rupt will be generated only if the UDRIE bit is written to one, the Global Interrupt Flag in
SREG is written to one and the UDRE bit in UCSRA is set.
• Bit 4 – RXEN: Receiver Enable
Writing this bit to one enables the USART Receiver. The Receiver will override normal
port operation for the RxD pin when enabled. Disabling the Receiver will flush the
receive buffer invalidating the FE, DOR and UPE Flags.
• Bit 3 – TXEN: Transmitter Enable
Writing this bit to one enables the USART Transmitter. The Transmitter will override nor-
mal port operation for the TxD pin when enabled. The disabling of the Transmitter
(writing TXEN to zero) will not become effective until ongoing and pending transmis-
sions are completed, i.e., when the Transmit Shift Register and Transmit Buffer Register
do not contain data to be transmitted. When disabled, the Transmitter will no longer
override the TxD port.
• Bit 2 – UCSZ2: Character Size
The UCSZ2 bits combined with the UCSZ1:0 bit in UCSRC sets the number of data bits
(character size) in a frame the Receiver and Transmitter use.
• Bit 1 – RXB8: Receive Data Bit 8
RXB8 is the ninth data bit of the received character when operating with serial frames
with nine data bits. Must be read before reading the low bits from UDR.
• Bit 0 – TXB8: Transmit Data Bit 8
TXB8 is the 9th data bit in the character to be transmitted when operating with serial
frames with 9 data bits. Must be written before writing the low bits to UDR.