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The 6502 Single Board Development System
Building An All-In-One 6502 Development Board
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Hexadecimal Value Display for 16 Bit Logic Input
Designing and Building a Hexadecimal Display for Small Computer and Logic Projects. I do digital design regularly, and it’s occasionally real handy to take a group of signals (e.g. an address bus) and display them. I don’t have a lot of great tools to do that though. Ordinarily I’d hook up my logic analyzer. That…
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Discrete VGA Graphics Adapter: Text Mode
Special Hardware for Plain old Text. Last time, I got my VGA circuit displaying an actual image. An off-color, artifact laden, not quite in the right place image, but an image nonetheless. Good enough to push the concept further, if nothing else. Text mode is exactly what it sounds like: a special mode for displaying…
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6502 Development: NOPerator Debugging Aid
A Very Simple 6502 Accessory That can Catch Very Complex bugs. Debugging is hard. Anyone who programs computers knows how hard it is to get stuff working reliably. Tiny oversights can lead to massive problems, often in ways that aren’t obvious. Patches get churned out on a daily basis. Hardware engineers have it much, much…
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Discrete VGA Graphics Adapter: Framebuffer and DAC
Putting Actual Graphics Into the Graphics Adapter Last time, I threw together a VGA time base. I didn’t spend much time elaborating on it, because honestly it bores me. There is only so much you can say about a counter that hasn’t already been said. This time around the goal is to display an actual…
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Discrete VGA Graphics Adapter: Time Base
Part 1: VGA Time Base Generation Ever since I started designing computers, I knew I needed to come up with some kind of graphics interface. Preferably one that didn’t require specialty hardware, licensing, or only worked with very old displays. There is one, and only one, interface that does the job: VGA. Despite being completely…
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HP 1660A Logic Analyzer Floppy Drive Replacement
Replacing an Obsolete Floppy Drive to Make an old Tool More Modern. Many, many years ago I scored an HP 1660A on eBay for 250 bucks. This is professional quality equipment that probably cost at least ten times that price when new. What a deal! Of course the reason I got it dirt cheap was…
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6502 Minimal Development Board
A Minimalist First Step Into Complex 6502 System Design. I’ve had a serious interest in computer hardware since high school. In between attempts to design my own CPU, I also took some interest in the 6502 shortly after finding Veronica. I promptly ordered two R65C02s- and did nothing with them. Keep in mind this was…
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Discrete PS/2 Keyboard Interface
Type Like it’s 1987: a Hardware Driven PS/2 Interface. In 1987 IBM released the PS/2 keyboard, an update of the earlier IBM AT keyboard with a smaller connector, extra features, and support for a mouse using the same connector and protocol. This rapidly became the standard for PC compatibles. You’ll still find PS/2 ports on…