Controlling the marquee

You should let the system ROM be in charge of controlling the marquee. But if you want to try things, here's how it goes:

See the bit definitions of the REG_LEDDATA and REG_LEDLATCHES registers for more details.

The system ROM uses ~35us delays done with fall-through calls to NOPs.

<synthaxhighlight> move.b #$FF, REG_LEDLATCHES  ; Set clock high jsr wait not.b d0  ; The panel # is sent inverted move.b d0, REG_LEDDATA  ; Set panel # move.b #$F7, REG_LEDLATCHES  ; Set clock low (latch panel #) jsr wait move.b #$FF, REG_LEDLATCHES  ; Set clock back high </syntaxhighlight>

<synthaxhighlight> wait: movem.l d0-d7/a0-a5,-(a7)  ; 120 cycles movem.l (a7)+,d0-d7/a0-a5  ; 124 cycles movem.l d0-d7/a0-a5,-(a7)  ; 120 cycles movem.l (a7)+,d0-d7/a0-a5  ; 124 cycles, total = 488 cycles = 40.7us </syntaxhighlight>