timer.c

来自「ARM公司ATC培训的所有练习源码」· C语言 代码 · 共 38 行

#include "timer.h"
#include "cortexm3.h"
#include "nvic.h"
#define MAGIC_VALUE 299999

#include <stdio.h>


void SysTick_init(void)
{
#if defined REAL_HARDWARE
	/*for Real Hardware, 1ms */
	int onems = ((NVIC.SysTick.Calibration) & 0x00ffffff);
	int reload = 999;  Supposed to be once a second (999+1 ms)

	/* If the calibration value is non 0 then we can use it as a more accurate value for 1ms */
	if(onems != 0)
	{
		reload = ((onems+1) * 1000)-1;
	}

	*SysTickLoad = reload;
#else
	*SysTickLoad = MAGIC_VALUE; /* Found to be more realistic on ISSM */
#endif

#if defined SYSTICK_INTERRUPT
	*SysTickCtrl = SysTickEnable | SysTickInterrupt; /* Start, with interrupts enabled */
#else
	*SysTickCtrl = SysTickEnable; /* Start, with interrupts enabled */
#endif
}

void SysTickHandler(void)
{
	printf("SysTick interrupt.\n\r");
}