I know the original post was a few years ago, but I decided to build a z80. Is there anyone that is currently in a build. I'm not building a kit of anything and am starting to string it up on bread board until I get something working. Have a bunch of ideas but I'm sure they are not new, but new to me. I have experience in electronics and programming in assembler and c. Plan on writing my own os and bios, but will start with cpm. Or the Linux version that was on it . Forgot the name at the moment.
I know the original post was a few years ago, but I decided to build a z80. Is there anyone that is currently in a build. I'm not building a kit of anything and am starting to string it up on bread board until I get something working. Have a bunch of ideas but I'm sure they are not new, but new to me. I have experience in electronics and programming in assembler and c. Plan on writing my own os and bios, but will start with cpm. Or the Linux version that was on it . Forgot the name at the moment.
I'm happy to observe and assist your with your progress in building a Z80 system from scratch.
I've done it many times to produce commercial (10,000+'s of units sold) and self interest projects.
If you're using a solderless breadboard the first step is to get the CPU bootstrapped.
The first things to do is to get the power supply, clock circuit, and temporary reset circuit up and working.
The relevant CPU input pins must be pulled up or down as necessary.
Your first program could be a LED flasher.
It consists of an LED with current limiting resistor connected to A15 with a 64K program consisting of just NOPs (0x00) that is hard wired to the data bus.
Once you've got that up and going it's time to add a proper reset circuit and add a ROM and associated decoding and (POJ) Power on Jump circuitry.
If you're planning to work with CP/M you need to ensure that RAM occupies the address space from 0x0000 when in CP/M operating mode.
One of the beauties of the Z80 is that you can have a RAMless system that runs useful programs.
Consider a useful debounced and delayed response reset button circuit rather than an instant reset circuit. This prevents an accidental touch of the reset button from resetting your system.
If you're very clever you may want to incorporate the patented "Special Reset" mode allowing you to run additional ICE (in circuit emulation) and testing software..
If you're a purist, have a look at the system clock signalling requirements and ensure that your clock circuit meets the specifications.
