15.12.6 USART Baud Rate 0 Register Low and High byte

The UBRR0L and UBRR0H register pair represents the 16-bit value, UBRR0.The low byte [7:0] (suffix L) is accessible at the original offset. The high byte [15:8] (suffix H) can be accessed at offset + 0x01. For more details on reading and writing 16-bit registers, refer to Accessing 16-bit Registers.

Name: UBRR0L and UBRR0H
Offset: 0x09
Reset: 0x00
Property: -

Bit 15141312111098 
     UBRR0[11:8] 
Access R/WR/WR/WR/W 
Reset 0000 
Bit 76543210 
 UBRR0[7:0] 
Access R/WR/WR/WR/WR/WR/WR/WR/W 
Reset 00000000 

Bits 11:0 – UBRR0[11:0] USART Baud Rate

This is a 12-bit register which contains the USART baud rate. The UBRR0H contains the four most significant bits and the UBRR0L contains the eight least significant bits of the USART 0 baud rate. Ongoing transmissions by the Transmitter and Receiver will be corrupted if the baud rate is changed. Writing UBRR0L will trigger an immediate update of the baud rate prescaler.