Rainbow Electronics ATmega128RFA1 - Manual (Page 374)

374
8266A-MCU Wireless-12/09
ATmega128RFA1
• Bit 5 – UDRE0 - USART Data Register Empty
The UDRE0 Flag indicates if the transmit buffer (UDR0) is ready to receive new data. If
UDRE0 is one, the buffer is empty, and therefore ready to be written. The UDRE0 Flag
can generate a Data Register Empty interrupt (see description of the UDRIE0 bit).
UDRE0 is set after a reset to indicate that the Transmitter is ready.
24.6.4 UCSR0B – USART0 MSPIM Control and Status Register B
Bit 7 6 5 4 3 2 1 0
NA ($C1) RXCIE0 TXCIE0 UDRIE0 RXEN0 TXEN0 UCSR0B
Read/Write RW RW RW RW RW
Initial Value 0 0 1 0 0
• Bit 7 – RXCIE0 - RX Complete Interrupt Enable
Writing this bit to one enables interrupt on the RXC0 Flag. A USART Receive Complete
interrupt will be generated only if the RXCIE0 bit is written to one, the Global Interrupt
Flag in SREG is written to one and the RXC0 bit in UCSR0A is set.
• Bit 6 – TXCIE0 - TX Complete Interrupt Enable
Writing this bit to one enables interrupt on the TXC0 Flag. A USART Transmit Complete
interrupt will be generated only if the TXCIE0 bit is written to one, the Global Interrupt
Flag in SREG is written to one and the TXC0 bit in UCSR0A is set.
• Bit 5 – UDRIE0 - USART Data Register Empty Interrupt Enable
Writing this bit to one enables interrupt on the UDRE0 Flag. A Data Register Empty
interrupt will be generated only if the UDRIE0 bit is written to one, the Global Interrupt
Flag in SREG is written to one and the UDRE0 bit in UCSR0A is set.
• Bit 4 – RXEN0 - Receiver Enable
Writing this bit to one enables the USART Receiver in MSPIM mode. The Receiver will
override normal port operation for the RxD0 pin when enabled. Disabling the Receiver
will flush the receive buffer. Only enabling the receiver in MSPI mode (i.e. setting
RXEN0=1 and TXEN0=0) has no meaning since it is the transmitter that controls the
transfer clock and since only master mode is supported.
• Bit 3 – TXEN0 - Transmitter Enable
Writing this bit to one enables the USART Transmitter. The Transmitter will override
normal port operation for the TxD0 pin when enabled. The disabling of the Transmitter
(writing TXEN0 to zero) will not become effective until ongoing and pending
transmissions are completed, i.e., when the Transmit Shift Register and Transmit Buffer
Register do not contain data to be transmitted. When disabled, the Transmitter will no
longer override the TxD0 port.
24.6.5 UCSR0C – USART0 MSPIM Control and Status Register C
Bit 7 6 5 4 3 2 1 0
NA ($C2) UDORD0 UCPHA0 UCPOL0 UCSR0C
Read/Write RW RW RW
Initial Value 1 1 0
• Bit 2 – UDORD0 - Data Order