shtupc
Post By：2008-1-6 7:57:00 [只看该作者]
在 ETR100.cpp文件中，有一个NB_Delay函数，里面调用了ReadTimer0( )函数，而ReadTimer0( )函数中有一句cli关中断的指令，我想问一下，在关中断这段短暂的时间里，如果外部设备通过串口发送过来数据，会不会因为中断系统是关闭的而丢掉，如何解决，谢谢！
下面是这两个函数的程序：
void NB_Delay( unsigned int milliseconds )
{
unsigned long stop;
unsigned cur, prev;
prev = ReadTimer0( );
stop = prev + (milliseconds * MULTIPLIER);
cur = ReadTimer0( );
while( cur < stop )
{
if(cur < prev) /* Check for timer wraparound */
{
if (stop < TMR0SIZE) break;
stop -= TMR0SIZE;
}
prev = cur;
cur = ReadTimer0( );
}
}
unsigned int ReadTimer0( )
{
asm pushf /* Save interrupt flag */
asm cli /* Disable interrupts */
asm mov al,0h /* Latch timer 0 */
asm out 43h,al
dummy(); /* Waste some time */
asm in al,40h /* Counter --> bx */
asm mov bl,al /* LSB in BL */
dummy(); /* Waste some time */
asm in al,40h
asm mov bh,al /* MSB in BH */
asm mov ax, 0f533h /* */
asm sub ax, bx
asm mov bx, ax /* Need ascending counter */
asm popf /* Restore interrupt flag */
return( _BX );
}
下面是这两个函数的程序：
void NB_Delay( unsigned int milliseconds )
{
unsigned long stop;
unsigned cur, prev;
prev = ReadTimer0( );
stop = prev + (milliseconds * MULTIPLIER);
cur = ReadTimer0( );
while( cur < stop )
{
if(cur < prev) /* Check for timer wraparound */
{
if (stop < TMR0SIZE) break;
stop -= TMR0SIZE;
}
prev = cur;
cur = ReadTimer0( );
}
}
unsigned int ReadTimer0( )
{
asm pushf /* Save interrupt flag */
asm cli /* Disable interrupts */
asm mov al,0h /* Latch timer 0 */
asm out 43h,al
dummy(); /* Waste some time */
asm in al,40h /* Counter --> bx */
asm mov bl,al /* LSB in BL */
dummy(); /* Waste some time */
asm in al,40h
asm mov bh,al /* MSB in BH */
asm mov ax, 0f533h /* */
asm sub ax, bx
asm mov bx, ax /* Need ascending counter */
asm popf /* Restore interrupt flag */
return( _BX );
}
