[Ti ASM] z flag to carry flag

Timendus · Post by **Timendus** » Sat 28 Oct, 2006 1:20 pm

A question for all you optimization gurus: What is the fastest and easiest way to get the z flag to the carry flag? I currently do it like this, but I'm 100% sure it can be done easier, probably in one opcode

Code: Select all

ztoc:
	jp z,ztoc_zero
	ld a,$FF
	rla    ; rotate set bit in carry flag
	ret
ztoc_zero:
	xor a
	rla    ; rotate reset bit in carry flag
	ret

Timendus · Post by **Timendus** » Sat 28 Oct, 2006 1:23 pm

update:

Code: Select all

ztoc:
   jp z,ztoc_zero
   scf
   ret
ztoc_zero:
   scf
   ccf
   ret

CoBB · Post by **CoBB** » Sat 28 Oct, 2006 1:29 pm

My first idea would be something along your second version, but I’d use or a to clear the carry.

EDIT: second idea:

Code: Select all

scf
ret z ; or nz if you want to invert it
ccf
ret

It has the nice property of preserving S, Z and P/V too.

Timendus · Post by **Timendus** » Sat 28 Oct, 2006 2:01 pm

Ah, yes, nice one