Is anyone interested with the Z80?

I've been reading Retro Gamer magazine for the past few months and the ZX Spectrum is reference quite a bit.  Sine the magazine is from the UK I suppose this makes sense, however until then I really had not heard of this unit until reading the mag.  Building a DIY ZX Spectrum would be interesting to play the old games on.

There does seem to be quite a few projects for the Z80 on this website though:

http://www.z80.info/homebrew.htm

That is what I'm planning. This is just the beginning. I was just starting where I was. I first thing I want to get accomplished is to get memory working and a serial terminal working so I can play around with it. This project will probably never be complete, but just further along . There is a lot of things I want to do but have to take it in steps. This weekend I want to get status LEDs set up. Reading and writing from memory, write an archaic is and watch what it can do. Then upgrade and upgrade from there.

Was doing some thinking .I have transceivers between the CPU and the address and data buses. Is it necessary to have transceivers between the memory and the buses, since memory will almost always be involved in most of the bus usage, ie. Dma.? Dreams like there should not be too much draw on the bus keeping memory on it. The chips are only enabled when memory is being called for anyhow. They do you think?  

Rather than flash lights on the data bus, why not have a separate port to do that by connecting an 8 bit flip-flop to the data bus with its inputs connected to data bus and outputs to LEDs and current limiting resistors and wire its CLK input so that any OUT instruction writes to it.

Thank you. I have the z80 blinking address lines doing nops. Wired the ram and rom mod . Clock is working.  Build an eeprom written.   Hopefully put it all together  and flash some lights on the data bus tonight or tomorrow.  We will see.  I get side tracked easily. Lol .let the good times roll

G'day Rob!

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.

Good Luck!

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. 

Please post a photo of it!

Yes, not visited since the split. Saw the Bombe just after it was installed.

i still have a z80 eval kit idling at my home corner, not sure what if anybody do use it nowadays but if got such a forum for modern revitalized usage of it, will be interested

Bletchley Park and TnMOC are completely different entities, albeit on the same grounds.  The museum is fully open Thursdays, Saturdays and Sundays and Colossus, Tunny, Heath Robinson and the Bombe are open every day.

I can’t take photos unfortunately as the spare books are all boxed up, you’d have to visit - not practical from Australia granted!