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DirectPage and DirectPageIndirect

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scawful
2023-08-19 20:12:56 -04:00
parent 7dcbc7f83c
commit 536136d8c9
5 changed files with 49 additions and 67 deletions
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7
src/app/emu/cpu.cc
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@@ -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());