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 reading "Z80 Explorer"
This blog post describes the various tools that I use for both work and hobby projects on my development PC.
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.
...continue reading "ZX Spectrum ROM mods"
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 a moment? Let's recreate an old computer and load in and play some games!
...continue reading "ZX Spectrum on FPGA using A-Z80 CPU"
This is a list of a some hard to find publications on the Z80 CPU.
...continue reading "Z80 Library"
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:
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 a dance of control signals in time.
This article is about making it all alive and kicking within an FPGA solution.
...continue reading "A Z80 : The Soul"
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 the Timing matrix - the mind of a CPU.
...continue reading "A Z80 : The Mind"
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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 generate machine cycles (M-cycles) and clock periods (T-states).
...continue reading "A Z80 : The Heart"