source: rtems/c/src/lib/libbsp/m68k/idp/timer/timer.c @ 88d594a

4.104.114.84.95
Last change on this file since 88d594a was 88d594a, checked in by Joel Sherrill <joel.sherrill@…>, on May 24, 1995 at 9:39:42 PM

Fully tested on all in-house targets

  • Property mode set to 100644
File size: 3.1 KB
Line 
1/*  Timer_init()
2 *
3 *  This routine initializes the MC68230 timer on the Motorola IDP board.
4 *
5 *  Input parameters:  NONE
6 *
7 *  Output parameters:  NONE
8 *
9 *  NOTE: This routine will not work if the optimizer is enabled
10 *        for some compilers.  The multiple writes to the MC68230
11 *        may be optimized away.
12 *
13 *        It is important that the timer start/stop overhead be
14 *        determined when porting or modifying this code.
15 *
16 *  Code Modified for the MC68230 by Doug McBride, Colorado Space Grant College
17 *
18 *  COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.
19 *  On-Line Applications Research Corporation (OAR).
20 *  All rights assigned to U.S. Government, 1994.
21 *
22 *  This material may be reproduced by or for the U.S. Government pursuant
23 *  to the copyright license under the clause at DFARS 252.227-7013.  This
24 *  notice must appear in all copies of this file and its derivatives.
25 *
26 *  $Id$
27 */
28
29
30#include <rtems.h>
31#include <bsp.h>
32#include <mc68230.h>
33
34#define TIMER_VECTOR 0x4D
35
36int Ttimer_val;
37rtems_boolean Timer_driver_Find_average_overhead;
38
39rtems_isr timerisr();
40
41void Timer_initialize()
42{
43  (void) set_vector( timerisr, TIMER_VECTOR, 0 );  /* install ISR */
44 
45  Ttimer_val = 0;                          /* clear timer ISR count */
46
47  /* some PI/T initialization stuff here */
48  /* Set up the interrupt vector on the MC68230 chip:
49     TIVR = TIMER_VECTOR; */
50  MC68230_WRITE (TIVR, TIMER_VECTOR);
51
52  /* Set CPRH through CPRL to maximum count to reduce interrupt overhead
53      CPRH = 0xFF;
54      CPRM = 0xFF;
55      CPRL = 0xFF; */
56  MC68230_WRITE (CPRH, 0xFF);
57  MC68230_WRITE (CPRM, 0xFF);
58  MC68230_WRITE (CPRL, 0xFF);
59
60  /* Enable timer and use it as an external periodic interrupt generator
61      TCR = 0xA1; */
62  MC68230_WRITE (TCR, 0xA1);
63
64}
65
66#define AVG_OVERHEAD      9  /* may not be right -- do this later */
67#define LEAST_VALID       10 /* Don't trust a value lower than this */
68
69int Read_timer() 
70{
71  rtems_unsigned8 data;
72  rtems_unsigned8  msb, osb, lsb;
73  rtems_unsigned32 remaining, total;
74
75  /* Disable timer so that timer can be read
76        data = TCR;
77        TCR = (data & 0xFE); */
78  MC68230_READ (TCR, data);
79  MC68230_WRITE (TCR, (data & 0xFE));
80
81  /* Read the counter value
82        msb = CNTRH;
83        osb = CNTRM;
84        lsb = CNTRL; */
85  MC68230_READ (CNTRH, msb);
86  MC68230_READ (CNTRM, osb);
87  MC68230_READ (CNTRL, lsb);
88
89  /* Calculate the time so far */
90  remaining = 0x1000000 - ((msb << 16) + (osb << 8) + lsb);
91  total = (Ttimer_val * 0x1000000) + remaining;
92
93  /* Enable timer so that timer can continue
94                TCR = 0xA1; */
95  MC68230_WRITE (TCR, 0xA1);
96
97  /* do not restore old vector */
98  if ( Timer_driver_Find_average_overhead == 1 )
99    return total;          /* in countdown units */
100
101  if ( total < LEAST_VALID )
102    return 0;            /* below timer resolution */
103   
104  /* Clocked at 6.5 Mhz */
105  /* Avoid floating point problems, be lazy, and return the total minus
106     the average overhead */
107  return (total - AVG_OVERHEAD);
108}
109
110rtems_status_code Empty_function( void )
111{
112  return RTEMS_SUCCESSFUL;
113}
114
115void Set_find_average_overhead(
116  rtems_boolean find_flag
117)
118{
119  Timer_driver_Find_average_overhead = find_flag;
120}
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