AxibugEmuOnline/Core/VirtualNes.Core/Mapper/Mapper073.cs

//////////////////////////////////////////////////////////////////////////
// Mapper073  Konami VRC3                                               //
//////////////////////////////////////////////////////////////////////////
using System;
using static VirtualNes.Core.CPU;
using static VirtualNes.MMU;
using BYTE = System.Byte;
using INT = System.Int32;


namespace VirtualNes.Core
{
    public class Mapper073 : Mapper
    {
        BYTE irq_enable;
        INT irq_counter;
        public Mapper073(NES parent) : base(parent)
        {
        }

        public override void Reset()
        {
            irq_enable = 0;
            irq_counter = 0;

            SetPROM_32K_Bank(0, 1, PROM_8K_SIZE - 2, PROM_8K_SIZE - 1);
        }

        //void Mapper073::Write(WORD addr, BYTE data)
        public override void Write(ushort addr, byte data)
        {
            switch (addr)
            {
                case 0xF000:
                    SetPROM_16K_Bank(4, data);
                    break;

                case 0x8000:
                    irq_counter = (irq_counter & 0xFFF0) | (data & 0x0F);
                    break;
                case 0x9000:
                    irq_counter = (irq_counter & 0xFF0F) | ((data & 0x0F) << 4);
                    break;
                case 0xA000:
                    irq_counter = (irq_counter & 0xF0FF) | ((data & 0x0F) << 8);
                    break;
                case 0xB000:
                    irq_counter = (irq_counter & 0x0FFF) | ((data & 0x0F) << 12);
                    break;
                case 0xC000:
                    irq_enable = (byte)(data & 0x02);
                    nes.cpu.ClrIRQ(IRQ_MAPPER);
                    break;
                case 0xD000:
                    nes.cpu.ClrIRQ(IRQ_MAPPER);
                    break;
            }
        }

        //void Mapper073::Clock(INT cycles)
        public override void Clock(int cycles)
        {
            if (irq_enable != 0)
            {
                if ((irq_counter += cycles) >= 0xFFFF)
                {
                    irq_enable = 0;
                    irq_counter &= 0xFFFF;
                    nes.cpu.SetIRQ(IRQ_MAPPER);
                }
            }
        }

        //void Mapper073::SaveState(LPBYTE p)
        public override void SaveState(byte[] p)
        {
            p[0] = irq_enable;
            //*(INT*)&p[1] = irq_counter;
            BitConverter.GetBytes(irq_counter).CopyTo(p, 1);
        }

        //void Mapper073::LoadState(LPBYTE p)
        public override void LoadState(byte[] p)
        {
            irq_enable = p[0];
            //irq_counter = *(INT*)&p[1];
            irq_counter = BitConverter.ToInt32(p, 1);
        }

        public override bool IsStateSave()
        {
            return true;
        }
    }
}