ATMEGA644PV ATMEL [ATMEL Corporation], ATMEGA644PV Datasheet - Page 189

• Manufacturer Part Number: ATMEGA644PV
• Description: 8-bit Microcontroller with 16/32/64K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

17.11.4
8011D–AVR–02/07
UCSRnC – USART Control and Status Register n C
• Bit 5 – UDRIEn: USART Data Register Empty Interrupt Enable n
Writing this bit to one enables interrupt on the UDREn Flag. A Data Register Empty interrupt will
be generated only if the UDRIEn 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 n
Writing this bit to one enables the USART Receiver. The Receiver will override normal port oper-
ation for the RxDn pin when enabled. Disabling the Receiver will flush the receive buffer
invalidating the FEn, DORn, and UPEn Flags.
• Bit 3 – TXENn: Transmitter Enable n
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 – UCSZn2: Character Size n
The UCSZn2 bits combined with the UCSZn1:0 bit in UCSRnC sets the number of data bits
(Character SiZe) in a frame the Receiver and Transmitter use.
• Bit 1 – RXB8n: Receive Data Bit 8 n
RXB8n 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 UDRn.
• Bit 0 – TXB8n: Transmit Data Bit 8 n
TXB8n is the ninth data bit in the character to be transmitted when operating with serial frames
with nine data bits. Must be written before writing the low bits to UDRn.
• Bits 7:6 – UMSELn1:0 USART Mode Select
These bits select the mode of operation of the USARTn as shown in
Table 17-4.
Note:
Bit
Read/Write
Initial Value
UMSELn1
1. See
0
0
1
1
operation
UMSELn1
UMSELn Bits Settings
R/W
”USART in SPI Mode” on page 196
7
0
UMSELn0
R/W
6
0
UMSELn0
0
1
0
1
UPMn1
R/W
5
0
UPMn0
Asynchronous USART
Synchronous USART
(Reserved)
Master SPI (MSPIM)
R/W
Mode
4
0
for full description of the Master SPI Mode (MSPIM)
ATmega164P/324P/644P
USBSn
R/W
3
0
UCSZn1
R/W
2
1
(1)
Table
UCSZn0
R/W
1
1
17-4..
UCPOLn
R/W
0
0
UCSRnC
189