It'd bit 7 of the F register, if you do anything to A that doesnt kill it (or a, or 0, and a, and $FF) then bit 7 of a is written into the S bit, and you could then use a conditional non-relative jump which has somehthing to do with the sign (eg: jp p,label or jp m,label).
Which is 4 T-states faster if you allready were using JP, and 1 or 5 T-states faster if you were using JR previously (depending on whether the condition in JR was true (5 faster) or false (1 faster))
so
Code: Select all
ld a,$FF
or a
jp P/M, label
Code: Select all
ld a,$FF
bit 7,a
jr z,label / jp z,label
Edit: I haven't tested it yet, but after OR, P/V is parity, so maybe it could be used instead of Bit 1,x?