9.2.9 _delay Builtin

A builtin function that delays execution.

Include

<xc.h>

Prototype

void _delay(unsigned long cycles);

Argument

cycles

The number of cycles to delay

Remarks

This is an inbuilt function that is expanded by the code generator. When called, this routine expands to an in-line assembly delay sequence. The sequence will consist of code that delays for the number of instruction cycles that is specified as the argument. The argument must be a constant expression that does not contain variables or function calls and that can be fully evaluated at compile time.

The _delay() builtin function can use loops and the nop instruction to implement the delay.

An error will result if the requested delay is not a constant expression or is greater than 50,463,240 instructions. For even larger delays, call this function multiple times.

Example

All of the inbuilt delay routines are shown in the following example.

#include <xc.h>

/* _XTAL_FREQ is defined by MCC headers; when not using MCC, place a definition similar to:
  #define _XTAL_FREQ 4000000
in your code to ensure that the 'us' and 'ms' forms of delay routines work as expected. */

unsigned char count;

void main(void) {
  SYSTEM_Initialize();

  while (1) {
    LATA = 0xFF;
    _delay(100);         /* wait 100 cycles*/
    LATA = 0xAA;
    _delaywdt(100);      /* wait 100 cycles, clearing the watchdog */
    LATA = 0x55;
    _delay3(10);         /* wait 30 cycles */
    LATA = 0xFF;
    __delay_us(800);     /* wait 800 micro seconds */
    LATA = 0x00;
    __delaywdt_us(800);  /* wait 800 micro seconds, clearing the watchdog */
    LATA = count;
    __delay_ms(500);     /* wait half a second */
    LATA = ~count;
    __delaywdt_ms(500);  /* wait half a second, clearing the watchdog */
    count++;
  }
}