[TI ASM] negating HL

[Duck]

Does anyone know a good way to negate HL? The way I'm doing it at the moment is:

ld a,h
neg
ld h,a
ld a,l
neg
ld l,a
ret

There are some undocumented instructions "XOR [HX/HY/LX/LY]" but i cant find information about them. Does anyone know what these do?

Thanks in advance.

[Kalimero]

ld a,h
neg
ld h,a
ld a,l
neg
ld l,a
ret

This doesn't always work. Try with 1 for example. You should just complement H and L with cpl and then increment HL.

There are some undocumented instructions "XOR [HX/HY/LX/LY]" but i cant find information about them. Does anyone know what these do?

I suspect these are the lower and higher bytes of ix and iy. Sometimes they are also referred to as ixh, ixl, iyh and iyl.

[CoBB]

I'd advise against using NEG at any time. CPL \ INC A is equivalent (both in size and time), and it opens more possibilities for optimisation.

As for the HX/LY notation, I also mention it in my guide. (At the beginning, where registers are explained.)

[Duck]

Oh yea of course, totally forgot about our lovely CPL. It was some time ago it wrote some assembly If even does the job better, flipping all bits in the byte. Thanks guys!