#include <MC68HC908QY4.h> /* include peripheral declarations */
#include <hidef.h>

void main(void) {
    byte pw;
    byte i;
    int adr, adr_;
    int conta;
	
    PTA = 0; /* clear/initialize Port A */

    /* do PWM */
    
    TSC_TSTOP = 1; // stop counter
    TSC_PS = 0;    // prescaler divide por 1
    TSC_TRST = 1;  // reset counter 
    TMODH =  0; TMODL = 250; // PWM frequency 20kHz
    TCH1H =  0; TCH1L =  50; // pulse width 
    TSC0_MS0B  = 0;  // PWM 
    TSC1_MS1A  = 1;  // output compare 
    TSC1_ELS1B = 1; TSC1_ELS1A = 0;  // clear on compare
    TSC1_TOV1  = 1;  // toggle on overflow
    TSC_TSTOP = 0;   // start counter

    /* do AD */
    ADSCR_CH = 2;     // entrada pino AD2=PTA4
    ADSCR_ADCO = 1;   // convert continously
    ADICLK_ADIV = 2;  // AD clock = 5MHz/4 (about 1MHz)
    
    adr_ = ADR-0x80;
  
    for(;;) {
    
    conta = 0;

      for(i=0;i<1000;i++) {
        while(!PTA_PTA1);
        adr = ADR-0x80;
        if(adr<=0 && adr_>0) conta++; // contar descidas por zero
        adr_ = adr;
        while(PTA_PTA1);
      }

    }
}