DRV USART BaudSet（）函数是否运行良好？

嗨，伙计们。我正在研究一个项目，希望能立即改变UART驱动程序的波特率。但是，当我使用它时，我会遇到同步问题。事实上，使用示波器，我注意到用DrviUsARTHARBUSET（）函数设置的BUDRAT是UXBRG值在纸上遇到的最坏的情况！所以我查看了DrviUsARTHARBUSET（）函数，我得到了这个函数：在这个代码中，我不理解这个部分：事实上，如果我设置第一个条件总是正确的，那么Boad Read总是高的。我错了吗？



      以下为原文

    Hi guys.
I'm working on a project that expects to change baudrate of the UART driver on the fly. But when I use it I have syncronizzation problems. In fact, using an osciloscope I noticed that the boudrate set with the DRV_USART_BaudSet() function is the worst confronted with the UxBRG value calcolate on the paper!
So I looked inside the DRV_USART_BaudSet() function and I reached this function:

DRV_USART_BAUD_SET_RESULT DRV_USART0_BaudSet(uint32_t baud)
{
    uint32_t clockSource;
    int32_t brgValueLow=0;
    int32_t brgValueHigh=0;
    DRV_USART_BAUD_SET_RESULT retVal = DRV_USART_BAUD_SET_SUCCESS;
#if defined (PLIB_USART_ExistsModuleBusyStatus)
    bool isEnabled = false;
#endif

    /* Get the USART clock source value*/
    clockSource = SYS_CLK_PeripheralFrequencyGet ( CLK_BUS_PERIPHERAL_2 );

    /* Calculate low and high baud values */
    brgValueLow = ( (clockSource/baud) >> 4 ) - 1;
    brgValueHigh = ( (clockSource/baud) >> 2 ) - 1;

#if defined (PLIB_USART_ExistsModuleBusyStatus)
        isEnabled = PLIB_USART_ModuleIsBusy (USART_ID_5);
        if (isEnabled)
        {
            PLIB_USART_Disable (USART_ID_5);
            while (PLIB_USART_ModuleIsBusy (USART_ID_5));
        }
#endif

    /* Check if the baud value can be set with high baud settings */
    if ((brgValueHigh >= 0) && (brgValueHigh <= UINT16_MAX))
    {
        PLIB_USART_BaudRateHighEnable(USART_ID_5);
        PLIB_USART_BaudRateHighSet(USART_ID_5,clockSource,baud);
    }
   
    /* Check if the baud value can be set with low baud settings */
    else if ((brgValueLow >= 0) && (brgValueLow <= UINT16_MAX))
    {
        PLIB_USART_BaudRateHighDisable(USART_ID_5);
        PLIB_USART_BaudRateSet(USART_ID_5, clockSource, baud);
    }
    else
    {
            retVal = DRV_USART_BAUD_SET_ERROR;
    }

#if defined (PLIB_USART_ExistsModuleBusyStatus)
    if (isEnabled)
    {
        PLIB_USART_Enable (USART_ID_5);
    }
#endif

    return retVal;
}

In this code I don't understand this part:

/* Check if the baud value can be set with high baud settings */
    if ((brgValueHigh >= 0) && (brgValueHigh <= UINT16_MAX))
    {
        PLIB_USART_BaudRateHighEnable(USART_ID_5);
        PLIB_USART_BaudRateHighSet(USART_ID_5,clockSource,baud);
    }
   
    /* Check if the baud value can be set with low baud settings */
    else if ((brgValueLow >= 0) && (brgValueLow <= UINT16_MAX))
    {
        PLIB_USART_BaudRateHighDisable(USART_ID_5);
        PLIB_USART_BaudRateSet(USART_ID_5, clockSource, baud);
    }
    else
    {
            retVal = DRV_USART_BAUD_SET_ERROR;
    }

In fact, if I set

brgValueLow = ( (clockSource/baud) >> 4 ) - 1;
brgValueHigh = ( (clockSource/baud) >> 2 ) - 1;

the first condition

if ((brgValueHigh >= 0) && (brgValueHigh <= UINT16_MAX))

is always true and than the Boud Rate High is always enabled.
Am I wrong?