DirectPage and DirectPageIndirect

src/app/emu/cpu.cc

@@ -54,8 +54,10 @@ int16_t CPU::FetchSignedWord() {
 }
 
 uint8_t CPU::FetchByteDirectPage(uint8_t operand) {
+  uint16_t distance = D * 0x100;
+
   // Calculate the effective address in the Direct Page
-  uint16_t effectiveAddress = D + operand;
+  uint16_t effectiveAddress = operand + distance;
 
   // Fetch the byte from memory
   uint8_t fetchedByte = memory.ReadByte(effectiveAddress);
@@ -81,8 +83,7 @@ void CPU::ExecuteInstruction(uint8_t opcode) {
       ADC(operand);
       break;
     case 0x65:  // ADC Direct Page
-      operand = FetchByteDirectPage(PC);
-      ADC(operand);
+      ADC(FetchByteDirectPage(PC));
       break;
     case 0x67:  // ADC DP Indirect Long
       operand = memory.ReadByte(DirectPageIndirectLong());

src/app/emu/cpu.h

@@ -75,7 +75,7 @@ class CPU : public Memory {
   // JMP (addr, X)
   uint16_t AbsoluteIndexedIndirect() {
     uint16_t address = FetchWord() + X;
-    return memory.ReadWord(address);
+    return memory.ReadWord(address & 0xFFFF);  // Consider PBR if needed
   }
 
   // Effective Address:
@@ -136,7 +136,10 @@ class CPU : public Memory {
   //    High/low: Direct Page Register plus operand byte
   //
   // LDA dp
-  uint16_t DirectPage() { return FetchByte(); }
+  uint16_t DirectPage() {
+    uint8_t dp = FetchByte();
+    return D + dp;
+  }
 
   // Effective Address:
   //    Bank:     Zero
@@ -168,7 +171,9 @@ class CPU : public Memory {
   // LDA (dp, X)
   uint16_t DirectPageIndexedIndirectX() {
     uint8_t dp = FetchByte();
-    return memory.ReadWord((dp + X) & 0xFF);
+    uint16_t effective_address = D + dp + X;
+    uint16_t indirect_address = memory.ReadWord(effective_address & 0xFFFF);
+    return indirect_address;
   }
 
   // Effective Address:
@@ -180,7 +185,9 @@ class CPU : public Memory {
   // LDA (dp)
   uint16_t DirectPageIndirect() {
     uint8_t dp = FetchByte();
-    return memory.ReadWord(dp);
+    // Add the Direct Page register to the fetched operand
+    uint16_t effective_address = D + dp;
+    return memory.ReadWord(effective_address);
   }
 
   // Effective Address:
@@ -191,7 +198,8 @@ class CPU : public Memory {
   // LDA [dp]
   uint16_t DirectPageIndirectLong() {
     uint8_t dp = FetchByte();
-    return memory.ReadWordLong(dp);
+    uint16_t effective_address = D + dp;
+    return memory.ReadWordLong(effective_address);
   }
 
   // Effective Address:
@@ -204,7 +212,8 @@ class CPU : public Memory {
   // LDA (dp), Y
   uint16_t DirectPageIndirectIndexedY() {
     uint8_t dp = FetchByte();
-    return memory.ReadWord(dp) + Y;
+    uint16_t effective_address = D + dp;
+    return memory.ReadWord(effective_address) + Y;
   }
 
   // Effective Address:
@@ -218,7 +227,8 @@ class CPU : public Memory {
   // LDA (dp), Y
   uint16_t DirectPageIndirectLongIndexedY() {
     uint8_t dp = FetchByte();
-    return memory.ReadWordLong(dp) + Y;
+    uint16_t effective_address = D + dp;
+    return memory.ReadWordLong(effective_address) + Y;
   }
 
   // 8-bit data: Data Operand Byte

src/app/emu/mem.h

@@ -9,20 +9,6 @@ namespace yaze {
 namespace app {
 namespace emu {
 
-class DirectPageMemory {
- public:
-  explicit DirectPageMemory(size_t size = 256) : memory_(size, 0) {}
-
-  uint8_t ReadByte(uint8_t address) const { return memory_[address]; }
-
-  void WriteByte(uint8_t address, uint8_t value) { memory_[address] = value; }
-
-  auto size() const { return memory_.size(); }
-
- private:
-  std::vector<uint8_t> memory_;
-};
-
 // memory.h
 class Memory {
  public:
@@ -55,16 +41,10 @@ class Memory {
 class MemoryImpl : public Memory {
  public:
   uint8_t ReadByte(uint16_t address) const override {
-    if (address < dp_memory_.size()) {
-      return dp_memory_.ReadByte(static_cast<uint8_t>(address));
-    }
     uint32_t mapped_address = GetMappedAddress(address);
     return memory_.at(mapped_address);
   }
   uint16_t ReadWord(uint16_t address) const override {
-    if (address < dp_memory_.size()) {
-      return dp_memory_.ReadByte(static_cast<uint8_t>(address));
-    }
     uint32_t mapped_address = GetMappedAddress(address);
     return static_cast<uint16_t>(memory_.at(mapped_address)) |
            (static_cast<uint16_t>(memory_.at(mapped_address + 1)) << 8);
@@ -172,9 +152,6 @@ class MemoryImpl : public Memory {
     }
   }
 
-  // Direct Page Memory
-  DirectPageMemory dp_memory_;
-
   // Define memory regions
   std::vector<uint8_t> rom_;
   std::vector<uint8_t> ram_;

src/app/emu/snes.h

@@ -13,8 +13,8 @@ namespace emu {
 
 class SNES {
  public:
-  SNES()=default;
-  ~SNES()=default;
+  SNES() = default;
+  ~SNES() = default;
 
   // Initialization
   void Init(ROM& rom);