/*****************************************************************************
 * Copyright (C) 2008
 * ProbeStar Telematics, LLC
 * All Rights Reserved.  Proprietary and Confidential.
 *============================================================================
 * Microsecond Delay Routine using Timer 0
 *----------------------------------------------------------------------------
 * 200nsec instruction cycle at 20Mhz, 100nsec at 40Mhz
 * You have to examine the asm output to count the instructions
 * Make sure this code is compiled with optimization -O -Zg4
*****************************************************************************/

/*****************************************************************************
 * includes
*****************************************************************************/

#include "system.h"
#include "delay.h"

/*****************************************************************************
 * defines
*****************************************************************************/

/*****************************************************************************
 * macros
*****************************************************************************/

/*****************************************************************************
 * structs & typedefs
*****************************************************************************/

/*****************************************************************************
 * global constants
*****************************************************************************/

/*****************************************************************************
 * global variables
*****************************************************************************/

// used by DelayUs() macro
LIBBANK volatile BYTE _dcnt = 0;

/*****************************************************************************
 * static constants
*****************************************************************************/

/*****************************************************************************
 * static variables
*****************************************************************************/

/*****************************************************************************
 * static prototypes
*****************************************************************************/

/*****************************************************************************
 * C functions
*****************************************************************************/

void DelayInit( void )
{
	// timer #0 as counter, 2 nsec counts (5 per usec)
#ifdef _PIC18
#if XTAL==40
	T0CON = 0b10000000;	// prescalar = 2
#else
	T0CON = 0b10001000;	// no prescalar
#endif
#else
	OPTION = 0b10000000;
#endif
}

// short delays up to 255 usec
void DelayUsec( BYTE n )
{
	// clear counter
#ifdef _PIC18
	TMR0H = 0;
	TMR0L = 0;
#else
	TMR0 = 0;
#endif
	// # ticks per usec
	n--;	// calling overhead
	n *= 5;

	// wait till count reaches
#ifdef _PIC18
	while ( TMR0L < n )
		;
#else
	while ( TMR0 < n )
		;
#endif
}

// longer delays up to 10000 usec (10 msec)
#ifdef _PIC18
void DelayUsecW( WORD n )
{
	// clear counter
	TMR0H = 0;
	TMR0L = 0;

	// 5 ticks per usec
	n--;		// calling overhead
	n *= 5;

	// wait till count reaches
	while ( TMR0 < n )
		;
}
#endif