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Fixed RESET functionality to emulate CPU behavior. #4

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Fixed RESET functionality to emulate CPU behavior. #4

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19 changes: 7 additions & 12 deletions 6502/6502Lib/src/private/m6502.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1139,23 +1139,18 @@ m6502::Word m6502::CPU::AddrIndirectY_6( s32& Cycles, const Mem& memory )
}


m6502::Word m6502::CPU::LoadPrg( const Byte* Program, u32 NumBytes, Mem& memory ) const
void m6502::CPU::LoadPrg( const Word LoadAddress, const Byte* Program, u32 NumBytes, Mem& memory ) const
{
Word LoadAddress = 0;
if ( Program && NumBytes > 2 )
{
u32 At = 0;
const Word Lo = Program[At++];
const Word Hi = Program[At++] << 8;
LoadAddress = Lo | Hi;
for ( Word i = LoadAddress; i < LoadAddress+NumBytes-2; i++ )
{
//TODO: mem copy?
memory[i] = Program[At++];
for ( Word i = 0; i < NumBytes; i++ )
{
memory[LoadAddress + i] = Program[i];
}
}

return LoadAddress;
// Set up the RESET vector
memory[0xFFFC] = LoadAddress & 0xFF;
memory[0xFFFD] = LoadAddress >> 8;
}

void m6502::CPU::PrintStatus() const
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12 changes: 4 additions & 8 deletions 6502/6502Lib/src/public/m6502.h
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Expand Up @@ -73,12 +73,8 @@ struct m6502::CPU

void Reset( Mem& memory )
{
Reset( 0xFFFC, memory );
}

void Reset( Word ResetVector, Mem& memory )
{
PC = ResetVector;
Word StartAddress = memory[0xFFFC] | memory[0xFFFD] << 8;
PC = StartAddress;
SP = 0xFF;
Flag.C = Flag.Z = Flag.I = Flag.D = Flag.B = Flag.V = Flag.N = 0;
A = X = Y = 0;
Expand Down Expand Up @@ -418,8 +414,8 @@ struct m6502::CPU
Flag.N = (Register & NegativeFlagBit) > 0;
}

/** @return the address that the program was loading into, or 0 if no program */
Word LoadPrg( const Byte* Program, u32 NumBytes, Mem& memory ) const;
/** Load a Program into memory at the given LoadAddress and set up the RESET vector to that location. */
void LoadPrg( const Word LoadAddress, const Byte* Program, u32 NumBytes, Mem& memory ) const;

/** printf the registers, program counter etc */
void PrintStatus() const;
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