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Cycle accuracy for a couple of the indexed write (store) instructions.

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Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2019-01-06 20:39:37 +00:00
parent 4d3be9e756
commit c3d2ef51d9
2 changed files with 22 additions and 3 deletions
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5
M6502/inc/mos6502.h
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@ -172,6 +172,11 @@ namespace EightBit {
void slo(uint8_t value);
void sre(uint8_t value);
// Complicated addressing mode implementations
void sta_AbsoluteX();
void sta_AbsoluteY();
uint8_t x = 0; // index register X
uint8_t y = 0; // index register Y
uint8_t a = 0; // accumulator

20
M6502/src/mos6502.cpp
View File

@ -250,7 +250,7 @@ int EightBit::MOS6502::execute() {
case 0x8f: Processor::busWrite(Address_Absolute(), A() & X()); break; // *SAX (absolute)
case 0x90: branch(!carry()); break; // BCC (relative)
case 0x91: addCycle(); Processor::busWrite(Address_IndirectIndexedY().first, A()); break; // STA (indirect indexed Y)
case 0x91: AM_IndirectIndexedY(); Processor::busWrite(A()); break; // STA (indirect indexed Y)
case 0x92: break;
case 0x93: break;
case 0x94: Processor::busWrite(Address_ZeroPageX(), Y()); break; // STY (zero page, X)
@ -258,11 +258,11 @@ int EightBit::MOS6502::execute() {
case 0x96: Processor::busWrite(Address_ZeroPageY(), X()); break; // STX (zero page, Y)
case 0x97: Processor::busWrite(Address_ZeroPageY(), A() & X()); break; // *SAX (zero page, Y)
case 0x98: busRead(); A() = through(Y()); break; // TYA (implied)
case 0x99: addCycle(); Processor::busWrite(Address_AbsoluteY().first, A()); break; // STA (absolute, Y)
case 0x99: sta_AbsoluteY(); break; // STA (absolute, Y)
case 0x9a: busRead(); S() = X(); break; // TXS (implied)
case 0x9b: break;
case 0x9c: break;
case 0x9d: addCycle(); Processor::busWrite(Address_AbsoluteX().first, A()); break; // STA (absolute, X)
case 0x9d: sta_AbsoluteX(); break; // STA (absolute, X)
case 0x9e: break;
case 0x9f: break;
@ -727,3 +727,17 @@ void EightBit::MOS6502::sre(const uint8_t value) {
busReadModifyWrite(lsr(value));
A() = eorr(A(), BUS().DATA());
}
//
void EightBit::MOS6502::sta_AbsoluteX() {
const auto [address, page] = Address_AbsoluteX();
getBytePaged(page, address.low);
Processor::busWrite(address, A());
}
void EightBit::MOS6502::sta_AbsoluteY() {
const auto [address, page] = Address_AbsoluteY();
getBytePaged(page, address.low);
Processor::busWrite(address, A());
}