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This project aims to build a system utilizing the Z80A and running CP/M-80 directly.

You might be wondering why I chose the Z80 today. Well, it happened to be discovered in my collection of electronic components after being tucked away for 30 years. Moreover, it’s an original Zilog Z80A from the NMOS process era, likely manufactured around 1980!

However, rather than simply replicating a single-board microcontroller system from the 1980s, I’ve decided to take a different approach. Reproducing such a system lacks novelty and excitement, not to mention the difficulty of sourcing the necessary parts.

Hence, I’ve devised the following design principles:

- A hybrid configuration utilizing both Z80A and ATmega128-16AU (AVR) microcontrollers.
- I won’t be using ROM; instead, a 64KB SRAM will be shared between the Z80A and AVR. AVR will manage the placement of the Z80’s bootstrap code.
- AVR firmware will handle the Z80 hardware I/O and interrupt cycles completely. Any Z80’s I/O devices can, in principle, be described by software!
- Design circuits using components that are as easy to procure as possible. (As of 2023, mainly in the Japanese electronic parts market.)”

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