Delay bug

[Guard]

PCWH 2.218
Hi,
on pin C4 I read 47KHz signal!
The steps are about 128x2uS (Toff) and 128x2uS (ton)!



#include <16f676.h>
#device adc=8
#use delay(clock=4000000)
#fuses NOWDT,INTRC, NOPROTECT,MCLR, NOCPD,PUT,BROWNOUT
#use fast_IO(c)

#byte portc=0x07
#byte porta=0x05
static int secondi;
static int A;
static long timers;
static short int start;
static long t;
static long Ton;
static long Toff;




void MsgErr(int Index );


void main()
{



setup_adc_ports(NO_ANALOGS|VSS_VDD);
setup_adc(ADC_OFF);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_16);
setup_timer_1(T1_DISABLED);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
disaBLE_INTERRUPTS(GLOBAL);


set_tris_c(15);
set_tris_a(12);

portc=0;
porta=0;




output_Low(PIN_C4);
delay_ms(500);

MsgErr(12);


}



void MsgErr(int Index )
{




do {


output_low(PIN_C4);
do {
t++;
delay_us(2);
} while (t<128);


output_High(PIN_C4);
do {
t++;
delay_us(2);
} while (t<128);



} while (1);



}

[ckielstra]

Your clock is running at 4MHz, resulting in 1 million instruction clock cycles per second --> 1 instruction clock cycle == 1 us.
Most instructions take 1 clock cycle, but some like 'goto' need 2 cycles.

Look at the list file below and you see the delay(2us) was coded with 2 NOP intructions, which is exactly 2 microseconds. The compiler is correct...