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/*  Timer_init()
 *
 *  This routine initializes TIMER 2 for an MC68302.
 *
 *  Input parameters:  NONE
 *
 *  Output parameters:  NONE
 *
 *  NOTE: It is important that the timer start/stop overhead be
 *        determined when porting or modifying this code.
 *
 *  COPYRIGHT (c) 1989-1999.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.OARcorp.com/rtems/license.html.
 *
 *  $Id: timer.c,v 1.2 2001-09-27 12:00:23 chris Exp $
 */
 
 
#include <rtems.h>
#include <bsp.h>
#include "m68302.h"
 
 
#define TMR2_VAL 0x071b /* Timer mode register
                         * (section 3.5.2.1 in 68302 manual)
                         * 15-8: "7"    prescaler divide by 8 (x+1)
                         *  7-6: 00     dis. intr. on capture event
                         *    5:  0      active-low pulse
                         *    4:  1     intr. on reaching reference
                         *    3:  1     restart counter on reference
                         *  2-1: 01     master clock input source
                         *    0:  1      enable timer
                         */
#define TRR2_VAL 2000   /* Timer reference register
                         * (section 3.5.2.2 in 68302 manual)
                         * 2000 ticks @ (16MHz/1)/8 = 1-ms count
                         */
 
rtems_unsigned32 Timer_interrupts;
 
rtems_boolean Timer_driver_Find_average_overhead;
 
rtems_isr timerisr();
 
void Timer_initialize( void )
{
    m302.reg.tmr2 = 0;                   /* disable timer */
 
    Timer_interrupts = 0;                /* clear timer ISR count */
 
    m302.reg.trr2 = TRR2_VAL;           /* set timer reference register */
    m302.reg.tmr2 = TMR2_VAL;           /* set timer mode register */
    m302.reg.imr |= RBIT_IMR_TIMER2;    /* set 68302 int-mask to allow ints */
}
 
/*
 *  The following controls the behavior of Read_timer().
 *
 *  FIND_AVG_OVERHEAD *  instructs the routine to return the "raw" count.
 *
 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
 *  is usually deducted from the number returned.
 *
 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
 *  below this are "noise" and zero is returned.
 */
 
#define AVG_OVERHEAD      0  /* It typically takes X.X microseconds */
                             /* (Y countdowns) to start/stop the timer. */
                             /* This value is in microseconds. */
#define LEAST_VALID       1  /* Don't trust a clicks value lower than this */
 
/*
 * Return timer value in 1/2-microsecond units
 */
int Read_timer( void )
{
  rtems_unsigned16 clicks;
  rtems_unsigned32 total;
 
  /*
   *  Read the timer and see how many clicks it has been since counter
   *  rolled over.
   */
 
  clicks = m302.reg.tcn2;
 
  /*
   *  Total is calculated by taking into account the number of timer overflow
   *  interrupts since the timer was initialized and clicks since the last
   *  interrupts.
   */
 
  total = (Timer_interrupts * TRR2_VAL) + clicks;
 
  if ( Timer_driver_Find_average_overhead == 1 )
    return total;          /* in XXX microsecond units */
 
  if ( total < LEAST_VALID )
    return 0;            /* below timer resolution */
 
  /*
   *  Convert 1/2-microsecond count into microseconds
   */
 
  return (total - AVG_OVERHEAD) >> 1;
}
 
 
/*
 *  Empty function call used in loops to measure basic cost of looping
 *  in Timing Test Suite.
 */
 
rtems_status_code Empty_function(void)
{
    return RTEMS_SUCCESSFUL;
}
 
void Set_find_average_overhead(
  rtems_boolean find_flag
)
{
  Timer_driver_Find_average_overhead = find_flag;
}

Line No.	Rev	Author	Line
1	30	unneback	`/* 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.OARcorp.com/rtems/license.html.`
18			`*`
19			`* $Id: timer.c,v 1.2 2001-09-27 12:00:23 chris Exp $`
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
43			`rtems_unsigned32 Timer_interrupts;`
44
45			`rtems_boolean Timer_driver_Find_average_overhead;`
46
47			`rtems_isr timerisr();`
48
49			`void 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			`*/`
80			`int 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
119			`rtems_status_code Empty_function(void)`
120			`{`
121			`return RTEMS_SUCCESSFUL;`
122			`}`
123
124			`void Set_find_average_overhead(`
125			`rtems_boolean find_flag`
126			`)`
127			`{`
128			`Timer_driver_Find_average_overhead = find_flag;`
129			`}`

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[/] [openrisc/] [trunk/] [rtos/] [rtems/] [c/] [src/] [lib/] [libbsp/] [m68k/] [ods68302/] [timer/] [timer.c] - Blame information for rev 173