Initial Commit

Bus.h

@@ -0,0 +1,28 @@
+//
+// Created by josh on 1/22/23.
+//
+
+#ifndef EMU6502_BUS_H
+#define EMU6502_BUS_H
+#include <cstdint>
+#include <array>
+
+
+
+#include "j6502.h"
+
+class Bus {
+public:
+    Bus();
+    ~Bus();
+public:
+    j6502 cpu;
+    std::array<uint8_t, 64*1024> ram;
+
+    void write(uint16_t addr, uint8_t data);
+
+    uint8_t read(uint16_t addr, bool readOnly);
+};
+
+
+#endif //EMU6502_BUS_H

CMakeLists.txt

@@ -0,0 +1,11 @@
+cmake_minimum_required(VERSION 3.24)
+project(emu6502)
+
+set(CMAKE_CXX_STANDARD 17)
+
+find_package(X11 REQUIRED)
+include_directories(${X11_INCLUDE_DIR})
+link_directories(${X11_LIBRARIES})
+
+add_executable(emu6502 main.cpp j6502.cpp j6502.h Bus.cpp Bus.h olcPixelGameEngine.h)
+target_link_libraries(emu6502 X11 GL png stdc++fs pthread)

j6502.h

@@ -0,0 +1,101 @@
+//
+// Created by josh on 1/22/23.
+//
+
+
+#ifndef EMU6502_J6502_H
+#define EMU6502_J6502_H
+
+#include <cstdint>
+#include <string>
+#include <vector>
+#include <map>
+
+
+typedef uint8_t u8;
+typedef uint16_t u16;
+typedef uint32_t u32;
+
+// Get Forward Declared
+class Bus;
+
+class j6502 {
+public:
+    enum FLAGS {
+        C = (1 << 0), // Carry Bit
+        Z = (1 << 1), // Zero
+        I = (1 << 2), // Disable Interrupts
+        D = (1 << 3), // Decimal Mode (unimplemented)
+        B = (1 << 4), // Break
+        U = (1 << 5), // Unused
+        V = (1 << 6), // Overflow
+        N = (1 << 7), // Negative
+    };
+    j6502();
+    ~j6502();
+    u8 status = 0x00; // Status Register
+    u8 a = 0x00; // Accumulator
+    u8 x = 0x00; // X Register
+    u8 y = 0x00; // Y Register
+    u8 sp = 0x00; // Stack Pointer
+    u16 pc = 0x0000; // Program Counter
+    // Facilitate emulation
+    u8 fetched = 0x00;
+    u16 addr_abs = 0x0000;
+    u16 addr_rel = 0x00;
+    u8 opcode = 0x00;
+    u8 cycles = 0;
+    uint32_t clock_count = 0;
+    u16 temp = 0x00;
+
+    Bus *bus = nullptr;
+    struct INSTRUCTION {
+        std::string name;
+
+        u8 (j6502::*operate)(void) = nullptr;
+
+        u8 (j6502::*addrmode)(void) = nullptr;
+
+        u8 cycles = 0;
+    };
+    std::vector<INSTRUCTION> lookup;
+
+    void ConnectBus(Bus *n){ bus = n; };
+    u8 read(u16 addr);
+    void write(u16 addr, u8 d);
+    u8 GetFlag(FLAGS f);
+    void SetFlag(FLAGS f, bool v);
+    u8 fetch();
+
+    std::map<u16, std::string> disassemble(u16 start, u16 stop);
+
+    void nmi();
+    void irq();
+    void reset();
+    void clock();
+    u8 CLC();u8 CLD();
+    u8 ZP0();u8 ZPX();u8 ABS();u8 REL();
+    u8 ZPY();u8 IMM();u8 IMP();u8 ABX();
+    u8 STX();u8 STA();u8 SED();u8 SEC();
+    u8 RTS();u8 RTI();u8 ROR();u8 ROL();
+    u8 PLP();u8 PLA();u8 PHP();u8 PHA();
+    u8 BVS();u8 BVC();u8 BRK();u8 BPL();
+    u8 BNE();u8 BMI();u8 BIT();u8 BEQ();
+    u8 BCS();u8 BCC();u8 ASL();u8 SBC();
+    u8 ADC();u8 AND();u8 DEY();u8 DEX();
+    u8 DEC();u8 CPY();u8 EOR();u8 INC();
+    u8 INX();u8 INY();u8 JMP();u8 JSR();
+    u8 LDA();u8 LDX();u8 LDY();u8 LSR();
+    u8 ORA();u8 ABY();u8 IND();u8 IZX();
+    u8 IZY();u8 CLI();u8 CLV();u8 CMP();
+    u8 CPX();u8 SEI();u8 XXX();u8 NOP();
+
+    u8 TYA();u8 TXS();u8 TXA();
+    u8 TSX();
+    u8 TAY();u8 TAX();u8 STY();
+
+    bool complete();
+};
+
+
+#endif //EMU6502_J6502_H

main.cpp

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+#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;
+}