
197
8018P–AVR–08/10
ATmega169P
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 2:1 – UCSZn[1:0]: Character Size
The UCSZn[1:0] bits combined with the UCSZn2 bit in UCSRnB sets the number of data bits
(Character SiZe) in a frame the Receiver and Transmitter use.
Bit 0 – UCPOLn: Clock Polarity
This bit is used for synchronous mode only. Write this bit to zero when asynchronous mode is
used. The UCPOLn bit sets the relationship between data output change and data input sample,
and the synchronous clock (XCK).
Table 19-9.
UPM Bits Settings
UPMn1
UPMn0
Parity Mode
00
Disabled
01
Reserved
1
0
Enabled, Even Parity
1
Enabled, Odd Parity
Table 19-10. USBSn Bit Settings
USBSn
Stop Bit(s)
01-bit
12-bit
Table 19-11. UCSZ Bits Settings
UCSZn2
UCSZn1
UCSZn0
Character Size
0
5-bit
0
1
6-bit
0
1
0
7-bit
0
1
8-bit
100
Reserved
101
Reserved
110
Reserved
1
9-bit
Table 19-12. UCPOLn Bit Settings
UCPOLn
Transmitted Data Changed
(Output of TxD Pin)
Received Data Sampled (Input on RxD
Pin)
0
Rising XCK Edge
Falling XCK Edge
1
Falling XCK Edge
Rising XCK Edge