os/kernel64/src/pit.c at main · reindeer002/os · GitHub

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#include "pit.h"
#include "assembly-utility.h"

void kInitializePIT(WORD wCount, BOOL bPeriodic) {
    kOutPortByte(PIT_PORT_CONTROL, PIT_COUNTER0_ONCE);
    if(bPeriodic) {
        kOutPortByte(PIT_PORT_CONTROL, PIT_COUNTER0_PERIODIC);
    }
    kOutPortByte(PIT_PORT_COUNTER0, wCount);
    kOutPortByte(PIT_PORT_COUNTER0, (wCount >> 8));
}

WORD kReadCounter0() {
    BYTE bHighByte, bLowByte;
    WORD wTemp = 0;

    kOutPortByte(PIT_PORT_CONTROL, PIT_COUNTER0_LATCH);

    bLowByte = kInPortByte(PIT_PORT_COUNTER0);
    bHighByte = kInPortByte(PIT_PORT_COUNTER0);
    wTemp = bHighByte;
    wTemp = (wTemp << 8) | bLowByte;

    return wTemp;
}

void kWaitUsingDirectPIT(WORD wCount) {
    WORD wLastCounter0;
    WORD wCurrentCounter0;

    kInitializePIT(0, TRUE);

    wLastCounter0 = kReadCounter0();
    while(1) {
        wCurrentCounter0 = kReadCounter0();
        if(((wLastCounter0 - wCurrentCounter0) & 0xFFFF) >= wCount) {
            break;
        }
    }
}