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#include "types.h"
#include "x86.h"
#include "defs.h"
#include "traps.h"
// Register definitions for the Intel
// 8253/8254/82C54 Programmable Interval Timer (PIT).
#define IO_TIMER1 0x040 // 8253 Timer #1
#define IO_TIMER2 0x048 // 8253 Timer #2 (EISA only)
// 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_CNTR0 (IO_TIMER1 + 0) // timer 0 counter port
#define TIMER_CNTR1 (IO_TIMER1 + 1) // timer 1 counter port
#define TIMER_CNTR2 (IO_TIMER1 + 2) // timer 2 counter port
#define TIMER_MODE (IO_TIMER1 + 3) // timer mode port
#define TIMER_SEL0 0x00 // select counter 0
#define TIMER_SEL1 0x40 // select counter 1
#define TIMER_SEL2 0x80 // select counter 2
#define TIMER_INTTC 0x00 // mode 0, intr on terminal cnt
#define TIMER_ONESHOT 0x02 // mode 1, one shot
#define TIMER_RATEGEN 0x04 // mode 2, rate generator
#define TIMER_SQWAVE 0x06 // mode 3, square wave
#define TIMER_SWSTROBE 0x08 // mode 4, s/w triggered strobe
#define TIMER_HWSTROBE 0x0a // mode 5, h/w triggered strobe
#define TIMER_LATCH 0x00 // latch counter for reading
#define TIMER_LSB 0x10 // r/w counter LSB
#define TIMER_MSB 0x20 // r/w counter MSB
#define TIMER_16BIT 0x30 // r/w counter 16 bits, LSB first
#define TIMER_BCD 0x01 // count in BCD
void
pit8253_timerinit(void)
{
// initialize 8253 clock to interrupt 100 times/sec
outb(TIMER_MODE, TIMER_SEL0 | TIMER_RATEGEN | TIMER_16BIT);
outb(IO_TIMER1, TIMER_DIV(100) % 256);
outb(IO_TIMER1, TIMER_DIV(100) / 256);
irq_enable(IRQ_TIMER);
}
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