Controlling the marquee: Difference between revisions
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Revision as of 05:58, 14 November 2017
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>