j6502/main.cpp

#include <iostream>
#include <cstdint>
#include <array>
#include <sstream>
#include <vector>

#include "Bus.h"
#include "j6502.h"

#define OLC_PGE_APPLICATION
#include "olcPixelGameEngine.h"



class Emulator : public olc::PixelGameEngine
{
public:
    Emulator() { sAppName = "olc6502 Demonstration"; }

    Bus nes;
    std::map<uint16_t, std::string> mapAsm;

    std::string hex(uint32_t n, uint8_t d)
    {
        std::string s(d, '0');
        for (int i = d - 1; i >= 0; i--, n >>= 4)
            s[i] = "0123456789ABCDEF"[n & 0xF];
        return s;
    };

    void DrawRam(int x, int y, uint16_t nAddr, int nRows, int nColumns)
    {
        int nRamX = x, nRamY = y;
        for (int row = 0; row < nRows; row++)
        {
            std::string sOffset = "$" + hex(nAddr, 4) + ":";
            for (int col = 0; col < nColumns; col++)
            {
                sOffset += " " + hex(nes.read(nAddr, true), 2);
                nAddr += 1;
            }
            DrawString(nRamX, nRamY, sOffset);
            nRamY += 10;
        }
    }

    void DrawCpu(int x, int y)
    {
        std::string status = "STATUS: ";
        DrawString(x , y , "STATUS:", olc::WHITE);
        DrawString(x  + 64, y, "N", nes.cpu.status & j6502::N ? olc::GREEN : olc::RED);
        DrawString(x  + 80, y , "V", nes.cpu.status & j6502::V ? olc::GREEN : olc::RED);
        DrawString(x  + 96, y , "-", nes.cpu.status & j6502::U ? olc::GREEN : olc::RED);
        DrawString(x  + 112, y , "B", nes.cpu.status & j6502::B ? olc::GREEN : olc::RED);
        DrawString(x  + 128, y , "D", nes.cpu.status & j6502::D ? olc::GREEN : olc::RED);
        DrawString(x  + 144, y , "I", nes.cpu.status & j6502::I ? olc::GREEN : olc::RED);
        DrawString(x  + 160, y , "Z", nes.cpu.status & j6502::Z ? olc::GREEN : olc::RED);
        DrawString(x  + 178, y , "C", nes.cpu.status & j6502::C ? olc::GREEN : olc::RED);
        DrawString(x , y + 10, "PC: $" + hex(nes.cpu.pc, 4));
        DrawString(x , y + 20, "A: $" +  hex(nes.cpu.a, 2) + "  [" + std::to_string(nes.cpu.a) + "]");
        DrawString(x , y + 30, "X: $" +  hex(nes.cpu.x, 2) + "  [" + std::to_string(nes.cpu.x) + "]");
        DrawString(x , y + 40, "Y: $" +  hex(nes.cpu.y, 2) + "  [" + std::to_string(nes.cpu.y) + "]");
        DrawString(x , y + 50, "Stack P: $" + hex(nes.cpu.sp, 4));
    }

    void DrawCode(int x, int y, int nLines)
    {
        auto it_a = mapAsm.find(nes.cpu.pc);
        int nLineY = (nLines >> 1) * 10 + y;
        if (it_a != mapAsm.end())
        {
            DrawString(x, nLineY, (*it_a).second, olc::CYAN);
            while (nLineY < (nLines * 10) + y)
            {
                nLineY += 10;
                if (++it_a != mapAsm.end())
                {
                    DrawString(x, nLineY, (*it_a).second);
                }
            }
        }

        it_a = mapAsm.find(nes.cpu.pc);
        nLineY = (nLines >> 1) * 10 + y;
        if (it_a != mapAsm.end())
        {
            while (nLineY > y)
            {
                nLineY -= 10;
                if (--it_a != mapAsm.end())
                {
                    DrawString(x, nLineY, (*it_a).second);
                }
            }
        }
    }

    bool OnUserCreate() override
    {
        // Load Program (assembled at https://www.masswerk.at/6502/assembler.html)
        /*
            *=$8000
            LDX #10
            STX $0000
            LDX #3
            STX $0001
            LDY $0000
            LDA #0
            CLC
            loop
            ADC $0001
            DEY
            BNE loop
            STA $0002
            NOP
            NOP
            NOP
        */

        // Convert hex string into bytes for RAM
        std::stringstream ss;
        ss << "A2 0A 8E 00 00 A2 03 8E 01 00 AC 00 00 A9 00 18 6D 01 00 88 D0 FA 8D 02 00 EA EA EA";
        uint16_t nOffset = 0x8000;
        while (!ss.eof())
        {
            std::string b;
            ss >> b;
            nes.ram[nOffset++] = (uint8_t)std::stoul(b, nullptr, 16);
        }

        // Set Reset Vector
        nes.ram[0xFFFC] = 0x00;
        nes.ram[0xFFFD] = 0x80;

        // Dont forget to set IRQ and NMI vectors if you want to play with those

        // Extract dissassembly
        mapAsm = nes.cpu.disassemble(0x0000, 0xFFFF);

        // Reset
        nes.cpu.reset();
        return true;
    }

    bool OnUserUpdate(float fElapsedTime)
    {
        Clear(olc::DARK_BLUE);


        if (GetKey(olc::Key::SPACE).bPressed)
        {
            do
            {
                nes.cpu.clock();
            }
            while (!nes.cpu.complete());
        }

        if (GetKey(olc::Key::R).bPressed)
            nes.cpu.reset();

        if (GetKey(olc::Key::I).bPressed)
            nes.cpu.irq();

        if (GetKey(olc::Key::N).bPressed)
            nes.cpu.nmi();

        // Draw Ram Page 0x00
        DrawRam(2, 2, 0x0000, 16, 16);
        DrawRam(2, 182, 0x8000, 16, 16);
        DrawCpu(448, 2);
        DrawCode(448, 72, 26);


        DrawString(10, 370, "SPACE = Step Instruction    R = RESET    I = IRQ    N = NMI");

        return true;
    }
};




int main() {
    Emulator demo;
    demo.Construct(680, 480, 2, 2);
    demo.Start();
    return 0;
}