314
8331B–AVR–03/12
Atmel AVR XMEGA AU
• Bit 2 – UDORD: Data Order
This bit is only for master SPI mode, and this bit sets the frame format. When written to one, the
lsb of the data word is transmitted first. When written to zero, the msb of the data word is trans-
mitted first. The receiver and transmitter use the same setting. Changing the setting of UDORD
will corrupt all ongoing communication for both receiver and transmitter.
• Bit 1 – UCPHA: Clock Phase
This bit is only for master SPI mode, and the bit determine whether data are sampled on the
leading (first) edge or tailing (last) edge of XCKn. Refer to the
”Master SPI Mode Clock Genera-
for details.
23.15.6
BAUDCTRLA – Baud Rate register A
• Bit 7:0 – BSEL[7:0]: Baud Rate Register
These are the lower 8 bits of the 12-bit BSEL value used for USART baud rate setting. BAUDC-
TRLB contains the four most-significant bits. Ongoing transmissions by the transmitter and
receiver will be corrupted if the baud rate is changed. Writing BSEL will trigger an immediate
update of the baud rate prescaler. See the equations in
23.15.7
BAUDCTRLB – Baud Rate register B
• Bit 7:4 – BSCALE[3:0]: Baud Rate Scale factor
These bits select the baud rate generator scale factor. The scale factor is given in two's comple-
ment form from -7 (0b1001) to +7 (0b0111). The -8 (0b1000) setting is reserved. See the
equations in
• Bit 3:0 – BSEL[11:8]: Baud Rate Register
These are the upper 4 bits of the 12-bit value used for USART baud rate setting. BAUDCTRLA
contains the eight least-significant bits. Ongoing transmissions by the transmitter and receiver
will be corrupted if the baud rate is changed. Writing BAUDCTRLA will trigger an immediate
update of the baud rate prescaler.
Bit
7
6
5
4
3
2
1
0
BSEL[7:0]
BAUDCTRLA
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
BSCALE[3:0]
BSEL[11:8]
BAUDCTRLB
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0