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A Z80 From the Ground Up
A-Z80 is a conceptual implementation of the venerable Zilog Z80 processor targeted to synthesize and run on a modern FPGA device. It differs from the existing (mostly Verilog) Z80 implementations in...
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A Z80 : The Heart
Click on any image to open a higher-resolution version. This is how it all works. The sequencer is "the heart" of a CPU. It gets the external clock which in turn toggles two rows of flip-flops that...
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A Z80 : The Mind
In the last article I described the sequencer, which is the heart of a CPU, and a few other blocks that perform various tasks. But how is it all orchestrated to perform useful work? Enter the PLA and...
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A Z80 : The Soul
In the first post I described the sequencer, a circuit that provided discrete timing signals to space operations apart. In the second post I mentioned the Timing matrix that was run by these signals...
View ArticleA Z80 : References
This design would not be possible without Ken Shirriff who reverse-engineered some major portions of Z80 from the picture of a die. These are the portions of the A-Z80 design that are based on his...
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Z80 Library
This is a list of a some hard to find publications on the Z80 CPU. 25 Microchips that Shook the World 8008 8-Bit CPU Architecture of a New Microprocessor Demystifying Microprocessor Design - M. Shima...
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ZX Spectrum on FPGA using A-Z80 CPU
In the last article I presented a different way of architecturally modelling a Zilog Z80 processor. It is time to do something really useful with it and what could be better than reliving the past for...
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The A-Z80 CPU
This article contains a brief overview and a background of the A-Z80 CPU created for FPGA boards and a ZX Spectrum implementation tied to it. (You can find the Russian translation of this article here:...
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ZX Spectrum ROM mods
In this blog I will show you how to interface an Atari-style joystick to the Altera DE1 FPGA board running a Spectrum implementation, how to change the ROM to enable you to input some game-cheat pokes...
View ArticleDevelopment PC Setup
This blog post describes the various tools that I use for both work and hobby projects on my development PC. Most people already have their own go-to tools for each new computer they start working...
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Z80 Explorer
Z80 Explorer is a Zilog Z80 netlist-level simulator capable of running Z80 machine code and also an educational tool with features that help reverse engineer and understand this chip better. Z80...
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A Calculator
Introduction The idea for this project came about during a week of freezing winter arctic event here in Austin, Texas, with a failed power grid as well as government, while keeping close to a gas...
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A Calculator (2): Basic Four Functions
This is the second article in a series on making our very own calculator. Introduction When I was in 13th grade, I almost flunked math. Test after test, I was getting poor grades and it seemed that I...
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A Calculator (3): Practical Numerical Methods
Introduction In the last post, we have verified and quantified the precision of the basic four functions (addition, subtraction, multiplication, and division), and now we can use them as a...
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A Calculator (4): The Framework
For as long as I remember, I had played with LEGOs. Those simple blocks would transform into complex objects whose final shape only existed in the supple thoughts of creative imagination. The kind of...
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A Calculator – Completed!
It has been a while since I wrote the last post about this project. In the meantime, I was able to dedicate all my free time to work on the implementation. As I was making really good progress, the...
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