> I'm Googling and I can't find much information about whether this is right... > has anyone done this before? What method did you use for the carry, half-carry > and overflow flags? (Not too bothered about half carry since I working on 68000, > but just curious for Z80). Noticed further down the board something was > mentioned about xoring all three for half carry? >
You didn't clearly mention which CPU you're having problems with, but I assume it's the Z80. Mine passes ZEXALL, this is what I did:
for 8-bit add/adc, sub/sbc (it's similar with 16-bit opcodes) A=accumulator d=data to be added/subtracted, excluding carry flag r=result after calculation
carry: simply A>r for add, A<r for sub (or if r>8bit: r>>8&1) half carry: like you said it's (r^A^d)&0x10 overflow: ((A^r)&(d^r))>>5&4 for add, ((A^d)&(A^r))>>5&4 for sub
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