calc84maniac wrote:
8-bit inc/dec do not touch the carry flag, and 16-bit inc/dec affect no flags at all.
Thanks calc84maniac. 
Once again we learn the wisdom of consulting the z80 guide before making assumptions. Once again we learn the wisdom of consulting the z80 guide before making assumptions. 
I ended up using CP skClear and taking out the whole overflow thing instead, although using LD HL, 0 and then ADD HL, DE would have set the carry/zero flag.
toraora wrote:
I ended up using CP skClear and taking out the whole overflow thing instead, although using LD HL, 0 and then ADD HL, DE would have set the carry/zero flag.
Yeah, but that's 4 bytes, where ld a,d \ or e \ ret z is a mere three bytes. 
Actually, another little-known fact is that 16-bit ADD does not affect the zero/overflow/sign flags. ADC and SBC do, though. But at any rate, adding 0 will never cause a carry. Adding 1 instead of using INC would detect carry just fine.
calc84maniac wrote:
Actually, another little-known fact is that 16-bit ADD does not affect the zero/overflow/sign flags. ADC and SBC do, though. But at any rate, adding 0 will never cause a carry. Adding 1 instead of using INC would detect carry just fine.
Thanks for the brain drain, calc84. Having never had to be that precise with such things, I should probably explore the specifics of these flags a bit more precisely. Register to Join the Conversation
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