6502/EightBit
1
0
Fork 0
mirror of https://github.com/MoleskiCoder/EightBit.git synced 2024-06-01 07:41:51 +00:00
Code Issues Projects Releases Wiki Activity

Correct BCD addition handling

Browse Source 
Signed-off-by: Adrian Conlon <adrian.conlon@gmail.com>
This commit is contained in:
Adrian Conlon 2021-10-30 21:25:56 +01:00
parent 04a9ffdcda
commit eeecb7c719
1 changed files with 17 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
M6502/src/mos6502.cpp
View File

@ -565,9 +565,7 @@ uint8_t EightBit::MOS6502::sub_d(const uint8_t operand, const uint8_t data, cons
}
uint8_t EightBit::MOS6502::adc(const uint8_t operand, const uint8_t data) noexcept {
const auto returned = add(operand, data, carry());
adjustNZ(m_intermediate.low);
return returned;
return add(operand, data, carry());
}
uint8_t EightBit::MOS6502::add(uint8_t operand, uint8_t data, int carry) noexcept {
@ -580,26 +578,32 @@ uint8_t EightBit::MOS6502::add_b(uint8_t operand, uint8_t data, int carry) noexc
P() = setBit(P(), VF, ~(operand ^ data) & (operand ^ m_intermediate.low) & NF);
P() = setBit(P(), CF, m_intermediate.high & CF);
adjustNZ(m_intermediate.low);
return m_intermediate.low;
}
uint8_t EightBit::MOS6502::add_d(uint8_t operand, uint8_t data, int carry) noexcept {
m_intermediate.word = operand + data + carry;
register16_t low = lowerNibble(operand) + lowerNibble(data) + carry;
register16_t high = higherNibble(operand) + higherNibble(data);
uint8_t low = lowNibble(operand) + lowNibble(data) + carry;
if (low > 9)
low += 6;
P() = clearBit(P(), ZF, (low + high).low);
uint8_t high = highNibble(operand) + highNibble(data) + (low > 0xf ? 1 : 0);
P() = setBit(P(), VF, ~(operand ^ data) & (operand ^ promoteNibble(high)) & NF);
if (low.word > 0x09) {
high += 0x10;
low += 0x06;
}
if (high > 9)
high += 6;
P() = setBit(P(), NF, high.low & NF);
P() = setBit(P(), VF, ~(operand ^ data) & (operand ^ high.low) & NF);
P() = setBit(P(), CF, high > 0xf);
if (high.word > 0x90)
high += 0x60;
return promoteNibble(high) | lowNibble(low);
P() = setBit(P(), CF, high.high);
return lowerNibble(low.low) | higherNibble(high.low);
}
uint8_t EightBit::MOS6502::andr(const uint8_t operand, const uint8_t data) noexcept {