>>Not entirely sure, but was it not to move a memory block?
Sure was! Used up HL, DE and BC to do it. Lots of stack operations needed in Z80 Assembly! The one I liked was the Restart Vectors that allowed a jump with one byte rather than three. Can make all the difference when you've got only 16K for everything (or 4K in the Level 1.) One of the RST was left free and entered RAM, the rest had fixed but useful ROM functions.
Just typing this reminds me of the smell of the softback book I pored over when using Edtasm. Those were heady days.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1