PS/2 mouse scroll wheel

Quote:

Here is Z3 though Z0 is a signed value, of the Z movement (scroll) if it is increased/ decreased with 2, then it is the vertical scroll wheel, else it is just the horizontal scroll wheel.

but what does it mean?

does it means:
odd values of Z (LSb set) are about vertical
even values (LSb clear) are about horizontal
means bit 0 indicates a displacement on V or H.

or:
if Z=(Z-1) +1 then, vertical
if Z=(Z-1) -1 then, idem

if Z=(Z-1) +2 then horizontal
if Z=(Z-1) -2 then idem

meaning can scroll only one position per frame...

or anything else?

because here, this explantations found everywhere in a cpy paste way is a little blur, there is not any illustraction to show what it is really.

i don't have this type of mouse at home, then, i cannot test..
maybe the touch pad is some emultation... i wonder...

thanks.

truth table for the dual scroll wheel Z field (bits 0 to 3 of 4th byte) 0 no scroll 1 one positive step on vertical scroll 2 one positive step on horizontal scroll 3 to D invalid E one négative step on horinzontal scroll F one négative step on vertical scroll