40 lines
1.1 KiB
C
40 lines
1.1 KiB
C
#include "timer.h"
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#include "isr.h"
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#include "tty.h"
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#include "../libc/string.h"
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#include "ports.h"
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// Start tick at zero
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uint32_t tick = 0;
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static void timer_callback(registers_t regs) {
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tick++;
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uint8_t buf[8];
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itoa(tick, buf, 10);
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kprint((uint8_t*)"Time: ");
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kprint((uint8_t*)buf);
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kprint((uint8_t*)"\n");
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// Cast to void unused parameter
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UNUSED_PAR(regs);
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}
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void init_timer(uint32_t frequency) {
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// Register a new ISR for IRQ0
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register_interrupt_handler(IRQ0, &timer_callback);
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/* As mentioned before, we'll send to PIT a value to divide for
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* his system clock(1.1931 MHz). We have to keep in mind that
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* this value must fit into a 16 bits variable */
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uint32_t divisor = 1193180 / frequency;
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// Send command to the right port
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outb(0x43, 0x36);
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// The two divisor has to be sent byte-wise, to do this we split them in two parts
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uint8_t low = (uint8_t)(divisor & 0xFF);
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uint8_t high = (uint8_t)((divisor >> 8) & 0xFF);
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// Send the frequency divisor
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outb(0x40, low);
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outb(0x40, high);
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} |