source: rtems/c/src/lib/libcpu/arm/lpc22xx/timer/timer.c @ c499856

4.11
Last change on this file since c499856 was c499856, checked in by Chris Johns <chrisj@…>, on Mar 20, 2014 at 9:10:47 PM

Change all references of rtems.com to rtems.org.

  • Property mode set to 100644
File size: 2.0 KB
Line 
1/*
2 * RTL22xx board Timer driver
3 *
4 * This uses Timer1 for timing measurments.
5 *
6 *  By Ray xu<rayx.cn@gmail.com>, modify form Mc9328mxl RTEMS DSP
7 *
8 *  The license and distribution terms for this file may be
9 *  found in the file LICENSE in this distribution or at
10 *  http://www.rtems.org/license/LICENSE.
11 *
12 * Notes:
13 *  This file manages the benchmark timer used by the RTEMS Timing Test
14 *  Suite.  Each measured time period is demarcated by calls to
15 *  benchmark_timer_initialize() and benchmark_timer_read().  benchmark_timer_read() usually returns
16 *  the number of microseconds since benchmark_timer_initialize() exitted.
17 *
18 *  It is important that the timer start/stop overhead be determined
19 *  when porting or modifying this code.
20*/
21
22#include <rtems.h>
23#include <bsp.h>
24#include <lpc22xx.h>
25#include "lpc_timer.h"
26uint32_t g_start;
27uint32_t g_freq;
28
29bool benchmark_timer_find_average_overhead;
30
31
32/*
33 * Set up Timer 1
34 */
35void benchmark_timer_initialize( void )
36{
37       g_freq = LPC22xx_Fpclk / 1000;
38}
39
40/*
41 *  The following controls the behavior of benchmark_timer_read().
42 *
43 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
44 *  is usually deducted from the number returned.
45 *
46 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
47 *  below this are "noise" and zero is returned.
48 */
49
50#define AVG_OVERHEAD      0  /* It typically takes X.X microseconds */
51                             /* (Y countdowns) to start/stop the timer. */
52                             /* This value is in microseconds. */
53#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
54
55int benchmark_timer_read( void )
56{
57  return (T0TC/(LPC22xx_Fpclk/1000000));
58  /*
59   *  Total is calculated by taking into account the number of timer overflow
60   *  interrupts since the timer was initialized and clicks since the last
61   *  interrupts.
62   */
63}
64
65void benchmark_timer_disable_subtracting_average_overhead(bool find_flag)
66{
67  benchmark_timer_find_average_overhead = find_flag;
68}
69
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