SendByte:
;E is the byte to send
;BC is the wait length
  ld a,3
  out (0),a
  ld d,a
_:
  in a,(0)
  and d
  jr nz,+_
  dec bc
  ld a,b
  or c
  jr nz,-_
  dec bc
  ret
_:
  ld b,8
SendByteLoop:
;E is the byte to send
;D is the mask
  xor a
  rlc e
  jr c,+_    ;could use rla
  inc a
_:
  out (0),a
  djnz SendByteLoop
  xor a
  out (0),a
  ld c,a
  ret