I just digged out one of my old projects…
I developed the Z80 board during my studies in electronic engineering as intermediate project. I was and I still am in love with my first computer, the Sinclair ZX81 which was equipped with a Zilog Z80 CPU. Later, I continued with an Amstrad CPC 464 and CPC 6128, also Z80A machines, for which I programmed 3D “demos” in assembler.
So building a Z80 computer from the scratch was one of the challenges that I wished to achieve. The schema has been designed with OrCAD (DOS version), the 2-layer PCB routed with Eagle (DOS version) and the board has been completely produced by hand craft (printing, UV exposing, etching).
The board boots from an EPROM and tries to contact a PC connected via the parallel Centronics port to download a software into the local RAM. Alternatively, the software can run from the EPROM directly. The LEDs allowed the software to communicate an OK signal, to show error codes or to just play around.