174
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P [DATASHEET]
8285E–AVR–02/2013
Bit 3 – TXENn: Transmitter Enable n
Writing this bit to one enables the USART Transmitter. The Transmitter will override normal port operation for the
TxD 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 Reg-
ister do not contain data to be transmitted. When disabled, the Transmitter will no longer override the TxD port.
Bit 2 – UCSZn2: Character Size n
The UCSZn2 bits combined with the UCSZ1n: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.
20.11.4
UCSRnC – USART Control and Status Register n C
Bit 6 – UMSELn: USART Mode Select n
This bit selects between asynchronous and synchronous mode of operation.
Bit 5:4 – UPMn[1:0]: Parity Mode
These bits enable and set type of parity generation and check. If enabled, the Transmitter will automatically gener-
ate and send the parity of the transmitted data bits within each frame. The Receiver will generate a parity value for
the incoming data and compare it to the UPM0n setting. If a mismatch is detected, the UPEn Flag in UCSRnA will
be set.
Bit 3 – USBSn: Stop Bit Select
This bit selects the number of stop bits to be inserted by the Transmitter. The Receiver ignores this setting.
Bit
765
432
10
(0xC2)
–
UMSELn
UPMn1
UPMn0
USBSn
UCSZn1
UCSZn0
UCPOLn
UCSRnC
Read/Write
R
R/W
Initial Value
000
001
10
Table 20-8.
UMSELn Bit settings.
UMSELn
Mode
0
Asynchronous Operation
1
Synchronous Operation
Table 20-9.
UPM Bits settings.
UPMn1
UPMn0
Parity mode
00
Disabled
01
Reserved
1
0
Enabled, Even Parity
1
Enabled, Odd Parity