1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
|
/* Timer_init()
*
* This routine initializes the timer on the FORCE CPU-386 board.
*
* Input parameters: NONE
*
* Output parameters: NONE
*
* NOTE: This routine will not work if the optimizer is enabled
* for some compilers. The multiple writes to the Z8036
* may be optimized away.
*
* It is important that the timer start/stop overhead be
* determined when porting or modifying this code.
*
* COPYRIGHT (c) 1989-1997.
* On-Line Applications Research Corporation (OAR).
* Copyright assigned to U.S. Government, 1994.
*
* The license and distribution terms for this file may in
* the file LICENSE in this distribution or at
* http://www.OARcorp.com/rtems/license.html.
*
* $Id$
*/
#include <rtems.h>
#include <bsp.h>
int Ttimer_val;
rtems_boolean Timer_driver_Find_average_overhead;
rtems_isr timerisr();
void Timer_initialize()
{
(void) set_vector( timerisr, 0x38, 0 ); /* install ISR */
Ttimer_val = 0; /* clear timer ISR count */
outport_byte( IERA, 0x40 ); /* disable interrupt */
outport_byte( TBCR, 0x40 ); /* stop the timer */
outport_byte( TBDR, 250 ); /* 250 units */
outport_byte( TBCR, 0x11 ); /* reset it, delay mode, 4X */
#if 0
outport_byte( TBCR, 0x13 ); /* reset it, delay mode, 16X */
#endif
outport_byte( IERA, 0x41 ); /* enable interrupt */
}
#define AVG_OVERHEAD 3 /* It typically takes 3.0 microseconds */
/* (3 ticks) to start/stop the timer. */
#define LEAST_VALID 4 /* Don't trust a value lower than this */
int Read_timer()
{
register rtems_unsigned32 clicks;
register rtems_unsigned32 total;
outport_byte( TBCR, 0x00 ); /* stop the timer */
inport_byte( TBDR, clicks );
total = Ttimer_val + 250 - clicks;
outport_byte( TBCR, 0x00 ); /* initial value */
outport_byte( IERA, 0x40 ); /* disable interrupt */
/* ??? Is "do not restore old vector" causing problems? */
if ( Timer_driver_Find_average_overhead == 1 )
return total; /* in one microsecond units */
else {
if ( total < LEAST_VALID )
return 0; /* below timer resolution */
return (total - AVG_OVERHEAD);
}
}
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;
}
|
