Controlling the marquee: Difference between revisions
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(Created page with "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|REG_LED...") |
m (Forgot RTS in subroutine) |
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The system ROM uses ~35us delays done with fall-through calls to NOPs. | The system ROM uses ~35us delays done with fall-through calls to NOPs. | ||
< | <syntaxhighlight> | ||
move.b #$FF, REG_LEDLATCHES ; Set clock high | move.b #$FF, REG_LEDLATCHES ; Set clock high | ||
jsr wait | jsr wait | ||
| Line 15: | Line 15: | ||
</syntaxhighlight> | </syntaxhighlight> | ||
< | <syntaxhighlight> | ||
wait: | wait: | ||
movem.l d0-d7/a0-a5,-(a7) ; 120 cycles | movem.l d0-d7/a0-a5,-(a7) ; 120 cycles | ||
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movem.l d0-d7/a0-a5,-(a7) ; 120 cycles | movem.l d0-d7/a0-a5,-(a7) ; 120 cycles | ||
movem.l (a7)+,d0-d7/a0-a5 ; 124 cycles, total = 488 cycles = 40.7us | movem.l (a7)+,d0-d7/a0-a5 ; 124 cycles, total = 488 cycles = 40.7us | ||
rts | |||
</syntaxhighlight> | </syntaxhighlight> | ||
[[Category:Code]] | [[Category:Code]] | ||
Latest revision as of 06:11, 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.
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 highwait:
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
rts