Figure 6.12-3 Auto-Baud Rate Measurement - Nuvoton ISD94124BYI Technical Reference Manual

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6.12.5.3 UART Controller Auto-Baud Rate Function Mode

The ISD94100 Auto-Baud Rate function measures the baud rate of in-coming data from UART RX pin

automatically. When the Auto-Baud Rate measurement is finished, the measuring baud rate is loaded

into BRD (UART_BAUD[15:0]).

Both BAUDM1 (UART_BAUD[29]) and BAUDM0 (UART_BAUD[28]) are set to 1 automatically. UART

RX data from Start bit to 1

detection frame.

bit time from Start bit to the 1

(UART_ALTCTL[20:19]). Setting ABRDEN (UART_ALTCTL[18]) is to enable auto-baud rate function.

In beginning stage, the UART RX is kept at 1. Once falling edge is detected, START bit is received. The

auto-baud rate counter is reset and starts counting. The auto-baud rate counter will be stop when the

rising edge is detected. Then, auto-baud rate counter value divided by ABRDBITS

(UART_ALTCTL[20:19])

(UART_ALTCTL[18]) is cleared. Once the auto-baud rate measurement is finished, the ABRDIF

(UART_FIFOSTS[1]) is set. When auto-baud rate counter is overflow, ABRDTOIF (UART_FIFOSTS[2])

is set. ABRDIF (UART_FIFOSTS[1]) or ABRDTOIF (UART_FIFOSTS[2]) cause the auto-baud rate flag

ABRIF(UART_ALTCTL[17])

ABRIF(UART_ALTCTL[17]) cause the auto-baud rate interrupt ABRINT (UART_INTSTS[31]) is

Rate Counter

(UART_FIFOSTS[1])

(UART_BAUD[15:0])

(UART_ALTCTL[18])

Programming Sequence Example:

Program ABRDBITS (UART_ALTCTL[20:19]) to determines UART RX data 1

edge time from Start by 2

Set ABRIEN (UART_INTEN[18]) to enable auto-baud rate function interrupt.

Set ABRDEN (UART_ALTCTL[18]) to enable auto-baud rate function.

ISD94100 Series Technical Reference Manual

rising edge time is set by 2

rising edge is calculated by setting ABRDBITS

(UART_BAUD[15:0])

... ... ... ... ... ... ... ... ...

keep old BRD

n = ABRDBITS (UART_ALTCTL[20:19])