Video: Setting the CPC screen with CRTC registers - Learn Z80 Lesson P39

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akuyou
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Video: Setting the CPC screen with CRTC registers - Learn Z80 Lesson P39

Post by akuyou » Tue Apr 23, 2019 3:04 am



CRTC registers define the position and shape of the screen.... they allow us to do crazy things, like resize and hardware scroll the screen... they also allow page flipping - and are generally responsible for the impressive demos the CPC has gained over recent years.
Lets check out the CRTC registers and see what they can do!

As always, this Video lesson matches the text lesson on my website, and you can get the source code as well...
http://www.chibiakumas.com/z80/platform4.php#LessonP39

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tricky
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Re: Video: Setting the CPC screen with CRTC registers - Learn Z80 Lesson P39

Post by tricky » Sat Sep 14, 2019 11:10 am

Nice intro to vertical rupture, I use it in most of my games on the BBC, so sorry for being slightly of off topic.
For Astro Blaster, I use it in a standard way to get a split screen with scrolling play area and a separate status area.
The other thing I use it for is displaying vertical arcade games in what would be 256x256 but only showing 224x256. This gives the original arcade resolution, whilst still making two consecutive rows of memory &200 apart, which, saves some cycles when drawing. As a bonus, the edges of the screen are clipped, so I can save some complication by not software clipping.
I think that this second use is more expensive on the CPC as I don't think it has the timers to get an interrupt every 16 scan lines.

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akuyou
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Re: Video: Setting the CPC screen with CRTC registers - Learn Z80 Lesson P39

Post by akuyou » Sat Sep 14, 2019 9:22 pm

Good point on the relevance to the BBC of this topic... I don't have the skill right now on the BBC side to cover this, but I'll be running out of prepared 6502 content soon, so maybe it's something I can start researching.
Chibi Akuma(s) Comedy-Horror 8-bit Bullet Hell shooter! // 「チビ悪魔」可笑しいゴシックSTG ! // Work in Progress: ChibiAliens

Interested in CPU's :Z80,6502,68000,6809,ARM,8086,RISC-V
Learning: 65816,ARM,8086,6809

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