tick_service.c

一个简单的小型操作系统

/*****************************************************************************
 *
 * Module      : tick_service.c
 * Description : Header File
 * Platform    : Evaluator7T
 * History     : 
 *
 * 2000-03-25 Andrew N. Sloss
 * - implemented a tick service
 *
 *****************************************************************************/


/*****************************************************************************
 * IMPORT
 *****************************************************************************/

#include "../headers/macros.h"

#include "../../headers/api_types.h"

/*****************************************************************************
 * MACRO'S
 *****************************************************************************/

/* none ... */
 
/*****************************************************************************
 * GLOBAL
 *****************************************************************************/

UINT countdown;

/*****************************************************************************
 * EXTERN's
 *****************************************************************************/

/* none... */

/*****************************************************************************
 * GLOBALS
 *****************************************************************************/

/* none... */

/*****************************************************************************
 * ROUTINES
 *****************************************************************************/

/* -- eventTickInit -----------------------------------------------------------
 *                                                            
 * Description  : Initialises the counter timer in milliseconds
 *
 * Parameters   : UINT msec - sets periodic timer in milliseconds
 * Return       : none...
 * Notes        : none...
 *                                                                             
 */
 
void eventTickInit (UINT msec)
{
/* ----------------------------------------------------------------------
 *
 * Initalize the Tick hardware on the Samsung part.
 *
 * ----------------------------------------------------------------------
 */

*TMOD = 0;
*INTPND = 0x00000000; 	// Clear pending interrupts .............

/* ----------------------------------------------------------------------
 *
 * Set the countdown value depending on msec.
 *
 * ----------------------------------------------------------------------
 */

  switch (msec)
  {
  case 2: /* fast ... */
  countdown = 0x000ffff0;
  break;
  default: /* slow ... */
  countdown = 0x00effff0;
  break;	
  }
}

/* -- eventTickService --------------------------------------------------------
 *
 * Description : interrupt service routine for timer0 interrupt.
 *
 * Parameters  : none...
 * Return      : none...
 * Notes       : 
 * 
 * timer interrupt everytime the counter reaches 0. To reset
 * the timer TDATA0 has to have a new initialization value.
 * Finally the last act is to unmask the timer interrupt on 
 * the Samsung KS3250C100.
 *
 */ 

#define tIOPDATA    (volatile unsigned int *)(SYSCFG + 0x5008)
#define LEDBANK     *tIOPDATA


#define LED_4_ON    LEDBANK |= 0x00000010
#define LED_4_OFF   LEDBANK = LEDBANK &~ 0x00000010

unsigned int xLED = 0;

 
void eventTickService(void) 
{ 

/* -- reset timer interrupt... */ 

*INTPND	= 1<<10;
*TDATA0	= countdown; 

  if (xLED==0)
  { 
  LED_4_ON; 
  xLED=1; 
  } 
  else 
  {
  LED_4_OFF; 
  xLED=0;
  } 

/* -- unmask the interrupt source.... */
	
*(volatile unsigned int*)INTMSK &= ~((1<<INT_GLOBAL)|(1<<10)|(1<<0));
} 

/* -- eventTickStart ----------------------------------------------------------
 *
 * Description  : switches on the periodic tick event
 *
 * Parameters   : none...
 * Return       : none...
 * Notes        : none...
 *
 */  
 
void eventTickStart(void)
{	
*TDATA0   = countdown; /* load Counter Timer ... */
*TMOD     |= 0x1;      /* enable interval interrupt ... */
  
/* -- unmask the interrupt source.. */ 
  	
*(volatile unsigned int*)INTMSK &= ~((1 << INT_GLOBAL) | (1<<10) | (1<<0));     
}