You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
45 lines
1.2 KiB
45 lines
1.2 KiB
#include <x86.h>
|
|
#include <trap.h>
|
|
#include <stdio.h>
|
|
#include <picirq.h>
|
|
|
|
/* *
|
|
* Support for time-related hardware gadgets - the 8253 timer,
|
|
* which generates interruptes on IRQ-0.
|
|
* */
|
|
|
|
#define IO_TIMER1 0x040 // 8253 Timer #1
|
|
|
|
/* *
|
|
* Frequency of all three count-down timers; (TIMER_FREQ/freq)
|
|
* is the appropriate count to generate a frequency of freq Hz.
|
|
* */
|
|
|
|
#define TIMER_FREQ 1193182
|
|
#define TIMER_DIV(x) ((TIMER_FREQ + (x) / 2) / (x))
|
|
|
|
#define TIMER_MODE (IO_TIMER1 + 3) // timer mode port
|
|
#define TIMER_SEL0 0x00 // select counter 0
|
|
#define TIMER_RATEGEN 0x04 // mode 2, rate generator
|
|
#define TIMER_16BIT 0x30 // r/w counter 16 bits, LSB first
|
|
|
|
volatile size_t ticks;
|
|
|
|
/* *
|
|
* clock_init - initialize 8253 clock to interrupt 100 times per second,
|
|
* and then enable IRQ_TIMER.
|
|
* */
|
|
void
|
|
clock_init(void) {
|
|
// set 8253 timer-chip
|
|
outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
|
|
outb(IO_TIMER1, TIMER_DIV(100) % 256);
|
|
outb(IO_TIMER1, TIMER_DIV(100) / 256);
|
|
|
|
// initialize time counter 'ticks' to zero
|
|
ticks = 0;
|
|
|
|
cprintf("++ setup timer interrupts\n");
|
|
pic_enable(IRQ_TIMER);
|
|
}
|
|
|