pit.cpp

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//
// Created on 7/5/20.
//

#include <pit.h>
#include <common.h>
#include <utilities.h>
#include <interrupt.h>
#include <ports.h>
#include <pic.h>

namespace INTRP
{
    extern DescriptorEntry idt_table[IDT_ENTRIES];

    void TimerInterruptHandler();
}

namespace TIMER
{
    uint64_t timer_ticks;

    enum PORT : uint8_t
    {
        CHANNEL_O = 0x40, 
        CHANNEL_1 = 0x41, 
        CHANNEL_2 = 0x42, 
        COMMAND   = 0x43  
    };

    enum CHANNEL : uint8_t
    {
        TIMER0 = 0x00, 
        TIMER1 = 0x40, 
        TIMER2 = 0x80  
    };

    enum ACCESSMODE : uint8_t
    {
        LATCH   = 0x00, 
        LO_ONLY = 0x10, 
        HI_ONLY = 0x20, 
        HI_LO   = 0x30  
    };

    enum OPMODE : uint8_t
    {
        COUNTDOWN             = 0x0, 
        ONESHOT               = 0x2, 
        RATE_GENERATOR        = 0x4, 
        SQUAREWAVE_GENERATOR  = 0x6, 
        SOFTWARE_STROBE       = 0x8, 
        HARDWARE_STROBE       = 0xA, 
        RATE_GENERATOR2       = 0xC, 
        SQUAREWAVE_GENERATOR2 = 0xE  
    };

    enum DECIMALMODE : uint8_t
    {
        BINARY = 0x0, 
        BCD    = 0x1  
    };

    const uint32_t BASE_FREQ        = 1'193'182; 
    const uint16_t TICKS_PER_SECOND = 1'000;

    void PIT_825x()
    {
        constexpr uint8_t PIT_SETTING = CHANNEL::TIMER0 | ACCESSMODE::HI_LO | OPMODE::SQUAREWAVE_GENERATOR | DECIMALMODE::BINARY;

        out8(PORT::COMMAND, PIT_SETTING);

        constexpr uint16_t timer_reload = (BASE_FREQ / TICKS_PER_SECOND);

        out8(PORT::CHANNEL_O, timer_reload & 0xFF);
        out8(PORT::CHANNEL_O, (timer_reload >> 8) & 0xFF);
    }
} // namespace TIMER

namespace INIT
{
    void PIT()
    {
        TIMER::PIT_825x();

        UnmaskInterrupt(INTRP::IVT::TIMER);
    }
}