40 lines
735 B
C
40 lines
735 B
C
#include "timer.h"
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#include "io.h"
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#include "sys.h"
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#include "idt.h"
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#define PIT_FREQUENCY 1193182
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#define PIT_CHANNEL_0 0x40
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#define PIT_COMMAND 0x43
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volatile uint32_t tick = 0;
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void pit_handler()
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{
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tick++;
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outb(0x20, 0x20);
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}
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void delay(uint32_t milliseconds)
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{
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uint32_t end = tick + milliseconds;
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while (tick < end)
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{
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sys_halt();
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}
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}
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void pit_set_frequency(uint32_t frequency)
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{
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uint32_t divisor = PIT_FREQUENCY / frequency;
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outb(PIT_COMMAND, 0x36);
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outb(PIT_CHANNEL_0, divisor & 0xFF);
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outb(PIT_CHANNEL_0, (divisor >> 8) & 0xFF);
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}
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void timer_install(void)
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{
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pic_remap(0x20, 0x28);
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pit_set_frequency(1000);
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idt_set_gate(32, (uint32_t)pit_handler_asm, 0x08, 0x8E);
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} |