6502/EightBit
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Refactor the 6502 code a little. No functional changes and tests still seem to work.

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Signed-off-by: Adrian Conlon <Adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2018-01-02 21:20:47 +00:00
parent 345ab2e2c6
commit 4d5afb67a3
4 changed files with 37 additions and 39 deletions
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16
M6502/inc/mos6502.h
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@ -61,9 +61,10 @@ namespace EightBit {
uint8_t SUB_b(uint8_t operand, uint8_t data, int borrow);
uint8_t SUB_d(uint8_t operand, uint8_t data, int borrow);
virtual void ADC(uint8_t data);
void ADC_b(uint8_t data);
void ADC_d(uint8_t data);
virtual uint8_t ADD(uint8_t operand, uint8_t data, int carry = 0);
uint8_t ADC(uint8_t operand, uint8_t data);
uint8_t ADD_b(uint8_t operand, uint8_t data, int carry);
uint8_t ADD_d(uint8_t operand, uint8_t data, int carry);
private:
void interrupt(uint8_t vector);
@ -318,8 +319,7 @@ namespace EightBit {
AM_ZeroPage(value);
break;
case 0b010:
assert(false);
break;
throw std::domain_error("Illegal addressing mode");
case 0b011:
AM_Absolute(value);
break;
@ -575,6 +575,12 @@ namespace EightBit {
AM_10(bbb, operand);
}
void DCP(int bbb) {
const auto result = AM_11_x(bbb) - 1;
setByte(result);
CMP(A(), result);
}
void ROR(uint8_t& output);
void LSR(uint8_t& output);

54
M6502/src/mos6502.cpp
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@ -303,7 +303,7 @@ int EightBit::MOS6502::execute(uint8_t cell) {
adjustNZ(A() ^= AM_01(decoded.bbb));
break;
case 0b011: // ADC
ADC(AM_01(decoded.bbb));
A() = ADC(A(), AM_01(decoded.bbb));
break;
case 0b100: // STA
AM_01(decoded.bbb, A());
@ -417,12 +417,8 @@ int EightBit::MOS6502::execute(uint8_t cell) {
case 0b101: // *LAX
adjustNZ(X() = A() = AM_11(decoded.bbb));
break;
case 0b110: { // *DCP
const auto operand = AM_11_x(decoded.bbb);
const auto result = SUB(operand, 1);
setByte(result);
CMP(A(), result);
}
case 0b110: // *DCP
DCP(decoded.bbb);
break;
case 0b111: // *SBC
A() = SBC(A(), AM_11(decoded.bbb));
@ -525,46 +521,42 @@ void EightBit::MOS6502::CMP(uint8_t first, uint8_t second) {
clearFlag(P(), CF, result.high);
}
void EightBit::MOS6502::ADC(uint8_t data) {
if (P() & DF)
ADC_d(data);
else
ADC_b(data);
uint8_t EightBit::MOS6502::ADC(const uint8_t operand, const uint8_t data) {
const auto returned = ADD(operand, data, P() & CF);
adjustNZ(MEMPTR().low);
return returned;
}
void EightBit::MOS6502::ADC_b(uint8_t data) {
register16_t sum;
sum.word = A() + data + (P() & CF);
adjustNZ(sum.low);
setFlag(P(), VF, ~(A() ^ data) & (A() ^ sum.low) & NF);
setFlag(P(), CF, sum.high & CF);
A() = sum.low;
uint8_t EightBit::MOS6502::ADD(uint8_t operand, uint8_t data, int carry) {
return P() & DF ? ADD_d(operand, data, carry) : ADD_b(operand, data, carry);
}
void EightBit::MOS6502::ADC_d(uint8_t data) {
auto carry = P() & CF;
uint8_t EightBit::MOS6502::ADD_b(uint8_t operand, uint8_t data, int carry) {
MEMPTR().word = operand + data + carry;
register16_t sum;
sum.word = A() + data + carry;
setFlag(P(), VF, ~(operand ^ data) & (operand ^ MEMPTR().low) & NF);
setFlag(P(), CF, MEMPTR().high & CF);
adjustNZ(sum.low);
return MEMPTR().low;
}
auto low = (uint8_t)(lowNibble(A()) + lowNibble(data) + carry);
uint8_t EightBit::MOS6502::ADD_d(uint8_t operand, uint8_t data, int carry) {
MEMPTR().word = operand + data + carry;
auto low = (uint8_t)(lowNibble(operand) + lowNibble(data) + carry);
if (low > 9)
low += 6;
auto high = (uint8_t)(highNibble(A()) + highNibble(data) + (low > 0xf ? 1 : 0));
setFlag(P(), VF, ~(A() ^ data) & (A() ^ promoteNibble(high)) & NF);
auto high = (uint8_t)(highNibble(operand) + highNibble(data) + (low > 0xf ? 1 : 0));
setFlag(P(), VF, ~(operand ^ data) & (operand ^ promoteNibble(high)) & NF);
if (high > 9)
high += 6;
setFlag(P(), CF, high > 0xf);
A() = (uint8_t)(promoteNibble(high) | lowNibble(low));
return (uint8_t)(promoteNibble(high) | lowNibble(low));
}
////

2
Ricoh2A03/inc/Ricoh2A03.h
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@ -14,6 +14,6 @@ namespace EightBit {
protected:
virtual uint8_t SUB(uint8_t operand, uint8_t data, int borrow) final;
virtual void ADC(uint8_t data) final;
virtual uint8_t ADD(uint8_t operand, uint8_t data, int carry) final;
};
}

4
Ricoh2A03/src/Ricoh2A03.cpp
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@ -9,6 +9,6 @@ uint8_t EightBit::Ricoh2A03::SUB(uint8_t operand, uint8_t data, int borrow) {
return MOS6502::SUB_b(operand ,data, borrow);
}
void EightBit::Ricoh2A03::ADC(uint8_t data) {
MOS6502::ADC_b(data);
uint8_t EightBit::Ricoh2A03::ADD(uint8_t operand, uint8_t data, int carry) {
return MOS6502::ADD_b(operand, data, carry);
}