At 12:42 22.09.98 -0500, you wrote:
>1) Why must that DEX thing be at the end of the Kill loop in order to draw
>a playfield?
If your sound loop runs through, X is set to 31. The KILL loop counts
down to 0 and waits for the scanline to finish between steps. This
way the Kill loop wastes 30 scanlines. Doing this is important to get
the timing of 60 frames per second done.
>2) Why is my playfield always black (it is on the sides of the screen.
>Difficult to see, but it is there)
You put a value of #3 into CTRLPF. This enables the reflect playfield
mode and the score colour mode. In the score colour mode the left half
of the playfield gets it's colour from COLUP0 and the right half gets
it's colour from COLUP1. Both these registers are set to zero.
>3)In regards to sound, when I delete the ; before the BNE, it doesn't give
>me the effect I want, which is a glissando thru all the frequency values.
>Is it going too fast? Have I forgot something?
It is way too fast. The VCS should do 60 frames per second with 262
scanlines per frame and 76 processor cycles per scanline. Your sound
routine steps through the frequency values in only a couple of cycles
and then waits for a full frame, before it does that again. To get the
effect, that you want, you must increase the AUDF0 value only once per
frame. You might need to store the counter in RAM for that.
Also your sound routine only goes from 10 to 31 and not through the
full frequency range.
Both the playfield and the sound code should be done during VBlank
or Overscan time. Vblank time would be in your code between the
STA VSYNC and the DRAW label.
Ciao, Eckhard Stolberg
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