Fast grayscale routine for thepenguin77

;###################################

#define FWAIT   in f, (c) \ jp m, $-2

grayCopy:
    push    ix
    ld  bc, (grayBC)
    ld  de, (grayDE)

    ld  ixl, C0h

outerGray:
    ld  a, ixl
    sub 40h
    FWAIT
    out ($10), a

    ld  a, $20
    FWAIT
    out ($10), a

    ld  ixh, 4

grayLoop:
    ld  a, (hl)
    inc hl
    xor (hl)
    and b
    xor (hl)
    inc hl

    FWAIT
    out ($11), a

    ld  a, (hl)
    inc hl
    xor (hl)
    and d
    xor (hl)
    inc hl

    FWAIT
    out ($11), a

    ld  a, (hl)
    inc hl
    xor (hl)
    and e
    xor (hl)
    inc hl

    FWAIT
    out ($11), a

    dec ixh
    jp  nz, grayLoop

    ld  a, b
    ld  b, d
    ld  d, e
    ld  e, a

    inc ixl
    jp  nz,outerGray



grayQuit:
    ld  (grayBC), bc
    ld  (grayDE), de
    pop ix
    ret