altera_avalon_timer_sc.c

来自「nios中自定义指令集实现三角函数的软件部分。」· C语言 代码 · 共 90 行

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#include <string.h>

#include "sys/alt_alarm.h"
#include "sys/alt_irq.h"

#include "altera_avalon_timer.h"
#include "altera_avalon_timer_regs.h"

#include "alt_types.h"
#include "sys/alt_log_printf.h"

/* 
 * alt_avalon_timer_sc_irq() is the interrupt handler used for the system 
 * clock. This is called periodically when a timer interrupt occurs. The 
 * function first clears the interrupt condition, and then calls the 
 * alt_tick() function to notify the system that a timer tick has occurred.
 *
 * alt_tick() increments the system tick count, and updates any registered 
 * alarms, see alt_tick.c for further details.
 */

static void alt_avalon_timer_sc_irq (void* base, alt_u32 id)
{
  /* clear the interrupt */

  IOWR_ALTERA_AVALON_TIMER_STATUS (base, 0);

  /* ALT_LOG - see altera_hal/HAL/inc/sys/alt_log_printf.h */
  ALT_LOG_SYS_CLK_HEARTBEAT();

  /* notify the system of a clock tick */
  alt_tick ();
}

/*
 * alt_avalon_timer_sc_init() is called to initialise the timer that will be 
 * used to provide the periodic system clock. This is called from the 
 * auto-generated alt_sys_init() function.
 */

void alt_avalon_timer_sc_init (void* base, alt_u32 irq, alt_u32 freq)
{
  /* set the system clock frequency */
  
  alt_sysclk_init (freq);
  
  /* set to free running mode */
  
  IOWR_ALTERA_AVALON_TIMER_CONTROL (base, 
            ALTERA_AVALON_TIMER_CONTROL_ITO_MSK  |
            ALTERA_AVALON_TIMER_CONTROL_CONT_MSK |
            ALTERA_AVALON_TIMER_CONTROL_START_MSK);

  /* register the interrupt handler, and enable the interrupt */
    
  alt_irq_register (irq, base, alt_avalon_timer_sc_irq);    
}