altera_avalon_timer_ts.c

nios中自定义指令集实现三角函数的软件部分。

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#include <string.h>

#include "system.h"
#include "sys/alt_timestamp.h"

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

#include "alt_types.h"

/*
 * These functions are only available if a timestamp device has been selected
 * for this system.
 */

#if (ALT_TIMESTAMP_CLK_BASE != none_BASE) 

/*
 * The function alt_timestamp_start() can be called at application level to
 * initialise the timestamp facility. In this case the period register is
 * set to full scale, i.e. 0xffffffff, and then started running. Note that
 * the period register may not be writable, depending on the hardware 
 * configuration, in which case this function does not reset the period.
 *
 * The timer is not run in continuous mode, so that the user can detect timer
 * roll-over, i.e. alt_timestamp() returns 0.
 *
 * The return value of this function is 0 upon sucess and -1 if in timestamp
 * device has not been registered. 
 */

int alt_timestamp_start(void)
{
  void* base = altera_avalon_timer_ts_base;

  if (!altera_avalon_timer_ts_freq)
  {
    return -1;
  }
  else
  {
    IOWR_ALTERA_AVALON_TIMER_CONTROL (base,
                    ALTERA_AVALON_TIMER_CONTROL_STOP_MSK);
    IOWR_ALTERA_AVALON_TIMER_PERIODL (base, 0xFFFF);
    IOWR_ALTERA_AVALON_TIMER_PERIODH (base, 0xFFFF);
    IOWR_ALTERA_AVALON_TIMER_CONTROL (base,
                                ALTERA_AVALON_TIMER_CONTROL_START_MSK);  
  }
  return 0;
}

/*
 * alt_timestamp() returns the current timestamp count. In the event that
 * the timer has run full period, or there is no timestamp available, this
 * function return -1.
 *
 * The returned timestamp counts up from the last time the period register
 * was reset. 
 */

alt_u32 alt_timestamp(void)
{
  alt_u32 lower;
  alt_u32 upper;

  void* base = altera_avalon_timer_ts_base;

  if (!altera_avalon_timer_ts_freq)
  {
    return 0xFFFFFFFF;
  }
  else
  {
    IOWR_ALTERA_AVALON_TIMER_SNAPL (base, 0);
    lower = IORD_ALTERA_AVALON_TIMER_SNAPL(base);
    upper = IORD_ALTERA_AVALON_TIMER_SNAPH(base);
    
    return (0xFFFFFFFF - ((upper << 16) | lower));   
  }
}

/*
 * Return the number of timestamp ticks per second. This will be 0 if no
 * timestamp device has been registered.
 */

alt_u32 alt_timestamp_freq(void)
{
  return altera_avalon_timer_ts_freq;
}

#endif /* timestamp available */