ATmega324P datasheet(207/377 Pages) ATMEL

207 / 377 page

207

7674F–AVR–09/09

ATmega164P/324P/644P

18.8.3

UCSRnB – USART MSPIM Control and Status Register n B

• Bit 7 - RXCIEn: RX Complete Interrupt Enable

Writing this bit to one enables interrupt on the RXCn Flag. A USART Receive Complete interrupt

will be generated only if the RXCIEn bit is written to one, the Global Interrupt Flag in SREG is

written to one and the RXCn bit in UCSRnA is set.

• Bit 6 - TXCIEn: TX Complete Interrupt Enable

Writing this bit to one enables interrupt on the TXCn Flag. A USART Transmit Complete interrupt

will be generated only if the TXCIEn bit is written to one, the Global Interrupt Flag in SREG is

written to one and the TXCn bit in UCSRnA is set.

• Bit 5 - UDRIE: USART Data Register Empty Interrupt Enable

Writing this bit to one enables interrupt on the UDREn Flag. A Data Register Empty interrupt will

be generated only if the UDRIE bit is written to one, the Global Interrupt Flag in SREG is written

to one and the UDREn bit in UCSRnA is set.

• Bit 4 - RXENn: Receiver Enable

Writing this bit to one enables the USART Receiver in MSPIM mode. The Receiver will override

normal port operation for the RxDn pin when enabled. Disabling the Receiver will flush the

receive buffer. Only enabling the receiver in MSPI mode (i.e. setting RXENn=1 and TXENn=0)

has no meaning since it is the transmitter that controls the transfer clock and since only master

mode is supported.

• Bit 3 - TXENn: Transmitter Enable

Writing this bit to one enables the USART Transmitter. The Transmitter will override normal port

operation for the TxDn pin when enabled. The disabling of the Transmitter (writing TXENn to

zero) will not become effective until ongoing and pending transmissions are completed, i.e.,

when the Transmit Shift Register and Transmit Buffer Register do not contain data to be trans-

mitted. When disabled, the Transmitter will no longer override the TxDn port.

• Bit 2:0 - Reserved Bits in MSPI mode

When in MSPI mode, these bits are reserved for future use. For compatibility with future devices,

these bits must be written to zero when UCSRnB is written.

Bit

210

RXCIEn

TXCIEn

UDRIE

RXENn

TXENn

UCSRnB

Read/Write

R/W

Initial Value

ATmega324P Datasheet(PDF) 207 Page - ATMEL Corporation

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