GetByte:
  ld d,3
  ld bc,-1
  xor a
  out (0),a
  in a,(0)
  xor d
  ret z
  ld bc,0800h
_:
  in a,(0)
  bit 1,a
  jr nz,-_
  out (0),a
  rra
  rl c
  djnz -_
  ret