AN3123 datasheet(12/30 Pages) STMICROELECTRONICS

12 / 30 page

Changing the UART baud rate on the fly

AN3123

12/30

Doc ID 16862 Rev 2

Changing the UART baud rate on the fly

The baud rate and line control registers (UARTIBRD, UARTFBRD and UARTLCR_H) form a

single 30-bit wide register named UARTLCR, which is updated on a single write strobe

generated by a UARTLCR_H write. So, in order to change the baud rate of the UART on the

fly, you need to perform the following two steps:

Modify the contents of the UARTIBRD and UARTFBRD registers as per the required

baud rate.

Perform a dummy write to the UARTLCR_H register.

4.1

Baud rate related registers

●

UART INTEGER BAUD RATE REGISTER (UARTIBRD) is a 16-bit RW register which

indicates the integer part of the baud rate divisor value.

Offset Value: ‘h024

●

UART FRACTIONAL BAUD RATE REGISTER (UARTFBRD) is a 16-bit RW register

which indicates the fractional part of the baud rate divisor value.

Offset Value: ‘h028

●

UART LINE CONTROL REGISTER (UARTLCR_H) is a 16-bit RW register which

accesses bits 29 to 22 of the UART bit rate and line control register UARTLCR.

Offset Value: ‘h02C

AN3123 Datasheet(PDF) 12 Page - STMicroelectronics