source: rtems/c/src/lib/libbsp/m68k/gen68302/timer/timer.c @ d6284ab

4.104.114.84.9
Last change on this file since d6284ab was d6284ab, checked in by Joel Sherrill <joel.sherrill@…>, on Sep 4, 2003 at 6:51:48 PM

2003-09-04 Joel Sherrill <joel@…>

  • clock/ckinit.c, console/console.c, include/bsp.h, include/coverhd.h, start/start.S, startup/bspclean.c, startup/bspstart.c, startup/linkcmds, timer/timer.c: URL for license changed.
  • Property mode set to 100644
File size: 3.2 KB
Line 
1/*  Timer_init()
2 *
3 *  This routine initializes TIMER 2 for an MC68302.
4 *
5 *  Input parameters:  NONE
6 *
7 *  Output parameters:  NONE
8 *
9 *  NOTE: It is important that the timer start/stop overhead be
10 *        determined when porting or modifying this code.
11 *
12 *  COPYRIGHT (c) 1989-1999.
13 *  On-Line Applications Research Corporation (OAR).
14 *
15 *  The license and distribution terms for this file may be
16 *  found in the file LICENSE in this distribution or at
17 *  http://www.rtems.com/license/LICENSE.
18 *
19 *  $Id$
20 */
21
22
23#include <rtems.h>
24#include <bsp.h>
25#include "m68302.h"
26
27
28#define TMR2_VAL 0x071b /* Timer mode register
29                         * (section 3.5.2.1 in 68302 manual)
30                         * 15-8: "7"    prescaler divide by 8 (x+1)
31                         *  7-6: 00     dis. intr. on capture event
32                         *    5:  0     active-low pulse
33                         *    4:  1     intr. on reaching reference
34                         *    3:  1     restart counter on reference
35                         *  2-1: 01     master clock input source
36                         *    0:  1     enable timer
37                         */
38#define TRR2_VAL 2000   /* Timer reference register
39                         * (section 3.5.2.2 in 68302 manual)
40                         * 2000 ticks @ (16MHz/1)/8 = 1-ms count
41                         */
42
43rtems_unsigned32 Timer_interrupts;
44
45rtems_boolean Timer_driver_Find_average_overhead;
46
47rtems_isr timerisr();
48
49void Timer_initialize( void )
50{
51    m302.reg.tmr2 = 0;                  /* disable timer */
52
53    Timer_interrupts = 0;               /* clear timer ISR count */
54
55    m302.reg.trr2 = TRR2_VAL;           /* set timer reference register */
56    m302.reg.tmr2 = TMR2_VAL;           /* set timer mode register */
57    m302.reg.imr |= RBIT_IMR_TIMER2;    /* set 68302 int-mask to allow ints */
58}
59
60/*
61 *  The following controls the behavior of Read_timer().
62 *
63 *  FIND_AVG_OVERHEAD *  instructs the routine to return the "raw" count.
64 *
65 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
66 *  is usually deducted from the number returned.
67 *
68 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
69 *  below this are "noise" and zero is returned.
70 */
71
72#define AVG_OVERHEAD      0  /* It typically takes X.X microseconds */
73                             /* (Y countdowns) to start/stop the timer. */
74                             /* This value is in microseconds. */
75#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
76
77/*
78 * Return timer value in 1/2-microsecond units
79 */
80int Read_timer( void )
81{
82  rtems_unsigned16 clicks;
83  rtems_unsigned32 total;
84
85  /*
86   *  Read the timer and see how many clicks it has been since counter
87   *  rolled over.
88   */
89
90  clicks = m302.reg.tcn2;
91
92  /*
93   *  Total is calculated by taking into account the number of timer overflow
94   *  interrupts since the timer was initialized and clicks since the last
95   *  interrupts.
96   */
97
98  total = (Timer_interrupts * TRR2_VAL) + clicks;
99
100  if ( Timer_driver_Find_average_overhead == 1 )
101    return total;          /* in XXX microsecond units */
102
103  if ( total < LEAST_VALID )
104    return 0;            /* below timer resolution */
105
106  /*
107   *  Convert 1/2-microsecond count into microseconds
108   */
109
110  return (total - AVG_OVERHEAD) >> 1;
111}
112
113
114/*
115 *  Empty function call used in loops to measure basic cost of looping
116 *  in Timing Test Suite.
117 */
118
119rtems_status_code Empty_function(void)
120{
121    return RTEMS_SUCCESSFUL;
122}
123
124void Set_find_average_overhead(
125  rtems_boolean find_flag
126)
127{
128  Timer_driver_Find_average_overhead = find_flag;
129}
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