Datasheet

198
8018P–AVR–08/10
ATmega169P
19.11.5 UBRRLn and UBRRHn – USART Baud Rate Registers
• Bit 15:12 – Reserved Bits
These bits are reserved for future use. For compatibility with future devices, these bit must be
written to zero when UBRRHn is written.
• Bit 11:0 – UBRR11:0: USART Baud Rate Register
This is a 12-bit register which contains the USART baud rate. The UBRRHn contains the four
most significant bits, and the UBRRLn contains the eight least significant bits of the USART
baud rate. Ongoing transmissions by the Transmitter and Receiver will be corrupted if the baud
rate is changed. Writing UBRRLn will trigger an immediate update of the baud rate prescaler.
Bit 151413121110 9 8
(0xC5) –––– UBRRn[11:8] UBRRHn
(0xC4) UBRRn[7:0] UBRRLn
76543210
Read/Write R R R R R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value00000000
00000000