How would I accomplish this?
The index registers replace HL register in instructions when combined with a prefix (for example, LD A,(HL) is $7E, LD A,(IX+d) is $DD $7E and LD A,(IY+d) is $FD $7E). As such you can't use HL and IX or IY in the same instruction.
Code:
This destroys DE and HL, so you may wish to push them onto the stack first and pop them back to restore them afterwards.
CP is (in effect) a subtraction that doesn't write the answer back to a register. Unfortunately there is no 16-bit CP. There is not even a straight-forwards 16-bit subtraction, only a subtract-with-carry, hence the use of SBC.
Code:
; Copy IX to DE.
push ix
pop de
; Subtract DE from HL
or a ; Clear carry flag
sbc hl,deThis destroys DE and HL, so you may wish to push them onto the stack first and pop them back to restore them afterwards.
CP is (in effect) a subtraction that doesn't write the answer back to a register. Unfortunately there is no 16-bit CP. There is not even a straight-forwards 16-bit subtraction, only a subtract-with-carry, hence the use of SBC.
Ahhh, that's what I was going to suggest (the push ix \ pop de), but I assumed that I might be able to come up with a better way, hence why this topic stayed open in a tab for my browser for two days and I didn't make a post.
If you want a faster solution that only destroys A (at the cost of a couple bytes and TI-Nspire compatibility):
Code:
If you don't need the Z flag output, a smaller solution (which still sacrifices TI-Nspire compatibility) is:
Code:
Code:
ld a,ixh
cp h
jr nz,_
ld a,ixl
cp l
_If you don't need the Z flag output, a smaller solution (which still sacrifices TI-Nspire compatibility) is:
Code:
ld a,ixl
sub l
ld a,ixh
sbc a,h
a you, TI! Register to Join the Conversation
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
Advertisement