Could somebody take a quick boo at this and tell me what's going wrong?
I'm just starting work on a new game idea I've been toying around
with and it's doing just fine on the emulator but not on a real 2600.
My playfield flashes for a brief moment halfway down the screen then
disappears to be replaced by a blank screen on a real 2600. On the
emulator everything looks just the way I wanted it to.
The timing seems off but as far as I can tell this is the same VBLANK
and overscan routine I've used on every program I've written to date.
And the graphics kernal (omitted for brevity) is just 192 scanlines
of nothing special. At this point all I was doing was manually plugging
in a playfield to see what it would look like. There was nothing wrong with
it as far as I can see.
Anyways, here's my VBLANK and Oscan routines....
main JSR vertb ;main loop
JSR draw
JSR clear
JMP main
vertb LDA #$02
STA VSYNC
STA WSYNC
STA WSYNC
LDA #$00
STA WSYNC
STA VSYNC
LDA #$2C
STA TIM64T
RTS
draw LDA INTIM ;check to see if it's time to draw a frame
BNE draw
sta WSYNC
sta VBLANK ;turn the screen on
;insert display kernal
rts
clear LDA #$25 ;set timer for overscan
STA TIM64T
LDA #$02 ;turn off the video
STA WSYNC
STA VBLANK
oscan LDA INTIM
bne oscan
sta WSYNC
rts
Apart from the zeroing routine and the graphics kernal this is all my
program is so far. And i haven't seen anything wrong with the graphics
kernal.
CRACKERS
(I seem to be going mad from hell!!!)
--
Collector of Atari 2600 carts - Accordionist - Bira Bira Devotee - Anime fan
* http://www.hwcn.org/~ad329/crab.html | Crackers' Arts Base *
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Nihongo ga dekimasu - 2600 programmer - Father of 2 great kids - Canadian eh
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