#pragma src(measure.a51)
#include <stdio.h>
#include <math.h>
#include <reg4051.h>

#define	XTAL	11.0592e6
#define BAUD	4800

typedef unsigned char u8;
typedef unsigned short u16;

u8	period_h;
u8	period_l;
u8	pulse_h;
u8	pulse_l;
bit	conversion_done;
u8 tl0_h;
u8 th0_h;


void int_tl0( void ) interrupt INT_T0	// count pulse
{
  tl0_h++;
}


void int_th0( void ) interrupt INT_T1	// count period
{
  if( ++th0_h == 200 ){
    IE0 = 0;
    EX0 = 1;				// enable next falling edge
  }
}


void int_ex0( void ) interrupt INT_EX0
{
  if( PX0 ){
#pragma asm
	xch	a, pulse_l		; save A
	clr	a
	xch	a, th0			; read and clear
	mov	period_l, a
	clr	a
	xch	a, tl0			; read and clear
	xch	a, pulse_l
#pragma endasm
    IE0 = 1;				// force calling again
    IP = PT0_ | PT1_;			// handle timers first
  }else{
    period_h = th0_h;
    th0_h = 0;
    pulse_h = tl0_h;
    tl0_h = 0;
    conversion_done = 1;
    EX0 = 0;				// disable
    IP = PX0_;				// restore priority
  }
}


void main (void)
{
  u16 period, pulse;
  PCON |= SMOD_;
  SCON = TI_ | REN_ | SM1_;
  TMOD = T0_M0_ | T0_M1_ | T0_GA_ | T1_M1_;
  TH1 = (u8) -(0.5 + XTAL / 12.0 / 16 / BAUD);
  TL1 = -1;
  TCON = TR0_ | TR1_ | IT0_;
  IP = PX0_;
  IE = ET0_ | ET1_ | EA_;

  printf( "Hallo Petern" );
  for(;;){ 						// main loop
    conversion_done = 0;
    while( conversion_done == 0 );
    period = (u16)period_h << 8 | period_l;
    pulse = (u16)pulse_h << 8 | pulse_l;
    printf("%8u", period );
    printf("%8u", pulse );
    printf("%8.2fn", 212.766 * ((float)pulse / period - 0.32) );
  }
}