我使用带有pca功能的51cpu

只看该作者 · 2009-10-15 22:24

使用捕获功能测的脉宽后，如何计算她的频率呢？因为pca的时基是分频得来的，所以有些搞不清初如何计算
51cpu的捕获功能例程
void PCA0_ISR (void) interrupt 11
{
static unsigned int current_capture_value, previous_capture_value;
static unsigned int capture_period;

if (CCF0)                         // If Module 0 caused the interrupt
{
   CCF0 = 0;                      // Clear module 0 interrupt flag.

   // Store most recent capture value
   current_capture_value = PCA0CP0;

   // Calculate capture period from last two values.
   capture_period = current_capture_value - previous_capture_value;

   // Update previous capture value with most recent info.
   previous_capture_value = current_capture_value;

}
else                               // Interrupt was caused by other bits.
{
   PCA0CN &= ~0x86;                // Clear other interrupt flags for PCA
}
}

还有下面一段pic的单片机测频的代码，我想转成51的
while( 1 )
{
setup_timer_1(T1_DISABLED);                         /* desabilita el timer 1 */
setup_ccp1(CCP_OFF);                                     /* desabilita el modo capture */
set_timer1(0);                                                    / * timer 1 cero */
CCP1IF = 0;                                                       /* capture flag cero */
setup_timer_1(T1_INTERNAL);                            /* activa timer 1 */
setup_ccp1(CCP_CAPTURE_DIV_16);                /* habilita modo capture */
while(!CCP1IF);                                                 /* Verifica si ocurrio captura */
temp1 = get_timer1();                                        /* Valor del TMR1 en temp1 */
CCP1IF = 0;                                                          / * capture flag = 0 */
while(!CCP1IF);                                                    /* Verifica si ocurrio captura */
temp2 = get_timer1();                                           /* Valor TMR1 en temp2 */
temp = temp2 - temp1;                                        /* valor TRM1 entre dos capturas */
temp1 = (16*1.0e6)/temp;                                     /* Temp1 = Frecuencia */

上面的pic代码十分简洁，大概意思和51cpu是一至的，关键在最后1行，频率是如何换算的？