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MidSpace Redux: Day 3


atari2600land

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So with it all nice and done, I went to test my MidSpace version 18 on a real Atari 2600 with my Harmony cart. To my horror, I discovered the screen jumped whenever I lost a life. This was I think at 9 this morning. I then spent the next at least hour and a half trying to fix it. Part of that went to changing the title screen tune since I wasn't really liking what I had in there then. I think my new song sounds more ominous. So after 90 minutes of working on the thing, I made the scanline count steady at 262. But one thing is bothering me with the Stella emulator. It says the scanline count is steady but when you go to test it on a Harmony cart, the screen jumps a little anyway. Why does that happen?

 

Nevertheless, I think I have it under control and working well.

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One thing to check is how you're setting VSYNC / VBLANK.  I have hazy memories of some people having problems with Skeleton which was eventually tracked down to how it did VSYNC / VBLANK (setting bits at the right time of the line and for the right number of lines).  Or was it I didn't use VBLANK, but just generated black.  Something or other.

 

There was also a bug in the original release of Skeleton+ which caused the "YOU WIN" screen to roll.  I wasn't paying attention when I was reordering the data in the cart and the label which I was using for the address of the last line wasn't anymore.

 

Maybe you've got something similar where you're jumping from one routine where the VSYNC is at the top of the loop to another where it's at the bottom.

 

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The way I fixed the jumping at 262 scanlines problem was by removing two lines of code, so perhaps I was doing too much at a certain time?

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23 hours ago, atari2600land said:

The way I fixed the jumping at 262 scanlines problem was by removing two lines of code, so perhaps I was doing too much at a certain time?

Yep, depending upon how you are counting lines that will do it.

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