UINT32 x;
    UINT8 x2;
    x = 10 * mFREQ_SYS / CH559UART1_BPS / 16;    //如果更改主频，注意x的值不要溢出                            
    x2 = x % 10;
    x /= 10;
    if ( x2 >= 5 ) x ++;                      //四舍五入

没有办法避免X2溢出啊