This is the second article in a series on making our calculator. This article is about prototyping and the verification of fundamental algorithms.
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Category: Retro
Stuff from the past.
A Calculator
The idea for this project came about during a week of freezing winter arctic events here in Austin, Texas, with a failed power grid (as well as the Texas government), while keeping close to a gas fireplace, the only source of heat and light, for a couple of days. With a weak internet over a phone data line, I could only do some preliminary searches and mainly work out various details on a writing pad, growing feeling that the project may be personally exciting and practically doable.
It took a long time, but this FPGA Calculator is now finished and I am really happy with how well it turned out.
Continue readingPlayZX
PlayZX is an Android application that lets you select from thousands of Sinclair ZX Spectrum games and play them through the headphone jack to load them onto your Speccy. You can also select your local (on the device) files, convert them to sound files, and then play them. This way, you can load games for the ZX Spectrum micro and a few other retro computers with a compatible audio jack.
Continue readingZ80 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.
Continue readingZX 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, and a few games I eventually completed using this setup.
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: https://howtorecover.me/z80-s-nulya)
ZX Spectrum on FPGA using A-Z80 CPU
In the last article, I presented a different way of architecturally modeling a Zilog Z80 processor. It is time to do something really useful with it and what could be better than reliving the past for a moment? Let’s recreate an old computer and load in and play some games!
Sinclair ZX Spectrum was my second computer, the first one being ZX81. As I was growing up in Croatia, I had a good friend whose brother, living in Germany, regularly sent him tapes with new games. Through this steady stream of games I’ve probably seen most of them (thank you, Krešo!) However, although I could, I had never played them through. Instead, I would load in DevPac – a debugger – and disassemble them trying to decipher how they were made and occasionally find some pokes for infinite lives.
Z80 Library
This is a list of some hard-to-find publications on the Z80 CPU.
A 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 work:
Continue readingA 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 and orchestrated the dance of control signals in time.
This article is about making it all alive and kicking within an FPGA solution.
