Category : C Source Code
Archive : R386DEV4.ZIP
Filename : TIMER.C
Output of file : TIMER.C contained in archive : R386DEV4.ZIP
/* Copyright 1992 by Dave Stampe and Bernie Roehl.
May be freely used to write software for release into the public domain;
all commercial endeavours MUST contact Bernie Roehl and Dave Stampe
for permission to incorporate any part of this software into their
products!
*/
#include
#include
#include
#include
#include
#include
/******************* TIMER INTERRUPT STUFF ****************/
#define TIMER_VECT 8 /* timer chip int. vector */
#define UNUSED_VECT 128 /* user vector: used to link to std ISR */
#define PIC_CMD 0x20 /* constants for PIC EOI command */
#define NONSPEC_EOI 0x20
#define TIMER_MODE 0x34 /* timer setup command */
#define TIMER_CONTROL 0x43 /* timer control register port */
#define TIMER_0 0x40 /* timer 0 port */
#define LATCH_COUNT 0x00 /* command to latch count */
#define SYNC_INTERVAL 5 /* how many frames between resynchronization */
static void init_SG_timer(int time);
static void reset_SG_timer();
static void interrupt fast_SG_timer();
static void interrupt (*oldint)() = NULL; /* old timer ISR vector */
static unsigned int clock_rate = 0; /* calibrated timer rate for vertical */
static unsigned int clock_rate_hi = 0;
static unsigned int clock_rate_lo = 0;
static unsigned int divisor = 0; /* counter to emulate 18.2 Hz tick */
static int syncount = SYNC_INTERVAL; /* resync counter */
static long int_timer = 0; /* incremented each frame (use for timing) */
static void (*frame_interrupt_routine)() = NULL;
static void (*glove_interrupt_routine)() = NULL;
static int glovecount = 0;
static int glove_rate = 2; /* count of how many glove calls per frame */
/******************* FIND VERTICAL FRAME RATE *************/
#define ADVANCE 100 /* time (microseconds) of advance */
/* in vert. interrupt. Will act as */
static int find_sega_speed() /* "vertical hold" adjustment */
{
unsigned int old, new; /* Routine to compute vertical frame */
vsync();
outportb(TIMER_CONTROL, TIMER_MODE);
outportb(TIMER_0, 0);
outportb(TIMER_0, 0); /* timer must count modulo 65536 */
disable(); /* time of vert. retrace */
vsync();
outportb(TIMER_CONTROL,LATCH_COUNT);
enable();
old = inportb(TIMER_0) & 0xFF;
old |= (inportb(TIMER_0) << 8);
vsync(); /* time 2 vert. retraces later */
disable();
vsync();
outportb(TIMER_CONTROL,LATCH_COUNT);
enable();
new = inportb(TIMER_0) & 0xFF;
new |= (inportb(TIMER_0) << 8);
return ((old-new)>>1) - ADVANCE; /* compute interrupt rate */
}
long current_time()
{
long i;
disable();
i = int_timer;
enable();
return i;
}
void set_current_time(long i)
{
disable();
int_timer = i;
enable();
}
volatile int interrupts_occurred = 0;
static void interrupt fast_SG_timer() /* NEW TIMER ISR */
{
unsigned int olddiv = divisor;
disable();
int_timer++;
interrupts_occurred++;
if (frame_interrupt_routine == NULL) goto glove;
else frame_interrupt_routine(glovecount-1);
if (--glovecount <= 0) glovecount = glove_rate;
else goto glove;
syncount--;
if (syncount < 0)
{
syncount = SYNC_INTERVAL;
outportb(TIMER_CONTROL, TIMER_MODE); /* stop timer */
outportb(TIMER_0, 255);
outportb(TIMER_0, 255);
enable();
disable();
vsync();
outportb(TIMER_CONTROL, TIMER_MODE); /* restart timer */
outportb(TIMER_0, clock_rate_lo);
outportb(TIMER_0, clock_rate_hi);
}
glove:
if (glove_interrupt_routine) glove_interrupt_routine();
divisor += clock_rate; /* dec divide count */
if (divisor < olddiv) /* simulate 18.2 Hz ISR if time */
geninterrupt(UNUSED_VECT);
outportb(PIC_CMD, NONSPEC_EOI);
enable();
}
static int ticks_per_second = 0;
int get_ticks_per_second()
{
return ticks_per_second;
}
static void reset_SG_timer();
static void init_SG_timer(int speed) /* SET UP FAST TIMER */
{
atexit(reset_SG_timer); /* set traps for error, ctrl c, */
signal(SIGABRT, reset_SG_timer);
signal(SIGFPE, reset_SG_timer);
signal(SIGINT, reset_SG_timer);
clock_rate = speed; /* save speed for future work */
ticks_per_second = 1190000L/speed;
clock_rate_hi = clock_rate >> 8;
clock_rate_lo = clock_rate & 255;
divisor = 0; /* set up timers */
syncount = SYNC_INTERVAL;
int_timer = 0;
if (getvect(UNUSED_VECT) == NULL)
{ /* setup int's if required(first run) */
disable();
oldint = getvect(TIMER_VECT); /* setup ISR vectors */
setvect(UNUSED_VECT,oldint);
setvect(TIMER_VECT, fast_SG_timer);
outportb(TIMER_CONTROL, TIMER_MODE); /* load timer */
outportb(TIMER_0, clock_rate_lo);
outportb(TIMER_0, clock_rate_hi);
enable();
}
}
static void reset_SG_timer() /* RESET PC TO NORMAL */
{
disable();
setvect(TIMER_VECT, oldint); /* reset vector */
outportb(TIMER_CONTROL, TIMER_MODE); /* reset timer */
outportb(TIMER_0, 0);
outportb(TIMER_0, 0);
setvect(UNUSED_VECT,NULL); /* disconnect flag */
enable();
signal(SIGINT, SIG_DFL);
signal(SIGABRT, SIG_DFL);
signal(SIGFPE, SIG_DFL);
}
/* SET EVERYTHING UP */
/* (init. glove, Sega first) */
void init_SG_interrupt( void (*sega_switcher)(), /* NULL if no sega/video */
void (*glove_handler)(), /* NULL if no glove driver */
int glove_tc) /* 1.19*uS (test interval) */
{ /* 6500 sugg. ALWAYS (fast timer) */
int i_rate;
glove_interrupt_routine = glove_handler;
frame_interrupt_routine = sega_switcher;
if (sega_switcher == NULL)
i_rate = glove_tc; /* glove only: use suggested speed */
else
{
i_rate = find_sega_speed(); /* use a multiple of video rate */
if (glove_tc != 0)
{
glove_rate = i_rate/glove_tc; /* about 2x for 72 fps, 3x for 60 */
if (glove_rate < 1) glove_rate = 1; /* handle no glove driver */
if (glove_rate > 20) glove_rate = 20; /* come on now... */
i_rate /= glove_rate;
}
else i_rate /=3;
}
init_SG_timer(i_rate); /* start 'er up! */
}
void init_timer()
{
init_SG_interrupt(NULL,NULL,6500);
}
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