Screen base in plotting code issue
Posted: Wed Dec 09, 2020 10:17 am
Hi,
Thought I'd jump back on here as I have a specific question regarding the screen plotting code from the Lesson 6 video (Lookup tables).
My question is, do the screen bases in that code just tell the program where to draw the graphics? Or does it actually set the visible screen?
I'm asking because I'm trying to draw a sprite to memory location &4000 (away from the visible screen, which is manually set at &C000 by setting Reg 12 of the CRTC to &30 which I believe is &C000), but it seems to be spilling over to the visible screen every 8 lines and then going back again (see picture link below).
https://drive.google.com/file/d/15vrQ5t ... sp=sharing
There's nothing in my code that points to &C000 (bar CRTC Reg 12) so I'm unsure what's happening. All I've done is set the main screen base in the plotting code to &40 and the jump back to the top to &4040 (256 wide screen). In fact, it seems to spill over to the visible screen no matter what base address I put in, or even what the CRTC Register is set to.
I've made some great leaps and bounds in the last while with my coding and my game, but this has stumped me for about 4 days now, so any help would be great!
Thanks!
Thought I'd jump back on here as I have a specific question regarding the screen plotting code from the Lesson 6 video (Lookup tables).
My question is, do the screen bases in that code just tell the program where to draw the graphics? Or does it actually set the visible screen?
I'm asking because I'm trying to draw a sprite to memory location &4000 (away from the visible screen, which is manually set at &C000 by setting Reg 12 of the CRTC to &30 which I believe is &C000), but it seems to be spilling over to the visible screen every 8 lines and then going back again (see picture link below).
https://drive.google.com/file/d/15vrQ5t ... sp=sharing
There's nothing in my code that points to &C000 (bar CRTC Reg 12) so I'm unsure what's happening. All I've done is set the main screen base in the plotting code to &40 and the jump back to the top to &4040 (256 wide screen). In fact, it seems to spill over to the visible screen no matter what base address I put in, or even what the CRTC Register is set to.
I've made some great leaps and bounds in the last while with my coding and my game, but this has stumped me for about 4 days now, so any help would be great!
Thanks!