Comment by jstanley

Definitely read (at least the first chapters of) the Z80 cpu manual: http://z80.info/zip/z80cpu_um.pdf

It gets a bit dry when it gets to the bit that documents the individual instructions, but the overview before that point is well worth reading.

Once you've done that and you're trying to write code, this page is a good reference for the instructions: http://clrhome.org/table/

To build a scavenged machine, you'll need a Z80 CPU, a clock source (I think an RC oscillator would be the simplest working setup?), probably some sort of ROM, an SRAM, some sort of IO device (probably a Z80 SIO/2 for serial), and a 5V power supply. I think that should be all that is required. Then you need to load your code into the ROM at address 0.

Then you can connect the SIO to a USB serial cable (e.g. FTDI) and communicate with your Z80 using a modern PC.

I can't remember if the SIO/2 needs external address decoding logic, maybe you could cope without it if you are happy for it to use up every address?

But building an RC2014 would be easier and more likely to result in a working machine, and would give you almost all the knowledge required to build a scavenged one later if you still want to.