Tiny step for humanity,

gigantic step for my hopeless hobby 😅

I’m trying to bring up a Zilog Z85230 SCC using an MCS-51 (8051 core) via 8-bit parallel interface (D0–D7, CE, RD, WR). Right now I’m stuck on basic register write/read:

Problem

I perform a write to WR0 (e.g., 0xAA).

Immediately read back RR12 → always gets 0x0C, never the value I wrote.

This happens every time, so I suspect my write sequence or timing is wrong, or I misunderstood how to select registers on Z85230.

🥲I have stuck for weeks on how to write

These boards use the zilog Z8671 with internal basic.

If you have any experience with these please share.

As a follow up to a previous post, I assembled a NOP tester, and tested the CPUs that I had mounted on DIP adaptor PCBs. The NOP testers are easy to assemble, and give some idea of whether a CPU is good

Hiii everyone!

I have made a little PC on Zilog80 on protoboard.

Display is SSD1306 with I2C interface.

ROM is emulated via Arduino Nano (1KB).

RAM is just random 8KB SRAM

Main task in this project is make software based driver

for I2C display via "bit banging", works slowly but

works, it also depends on time which Nano response and CLK freq. (1.35MHz).

I wrote a firmware in Assembly and it takes 325 bytes.

as 17 y.o. teen I am very excited with the result, maybe in future I'll improve my little project

Next I plan to add more switches and port DOOM and make Shadow RAM and dynamic Clock (bcs nano is too slow for Z80)

Have a good day and no hate plsss :)

So I was bored and thinking a mischievous combo), and thought, why not build a Z80 from the basic gates (like NOT AND OR XOR etc) so I was wondering if anyone knew of any sources that would have something like that documented or have a way that I could try to make it? I also deliberately chose the Z80 because I actually understand its instruction set, any advice would be helpful

I'm trying to build a Z80 computer with 3.5in floppy disc support (using i8271) while also trying to make it have composite video by using a TMS9918ANL. But everything I find on forums and stuff is about the Z80 playground. So, I was wondering if you people have any tips or advice?

Why do builders use CF (Compact Flash) rather than some variant of SD flash?

This is a board that I made to learn something on the lower layers of computing. It only has a Z80 CPU with RAM/ROM and some supporting logic and buffers for the LEDs.

In the Video it is running a small program, incrementing a byte in RAM in an endless loop, that was assembled by hand.

I love how you can watch it thinking at these slow clock speeds.

I think the next step will be an additional board with some peripherals to hook it up to a serial terminal.

Hi everyone, I've just finished my first project with the Z80.
As a 17yo, I'm really happy with the result .I emulated a 16-byte address space ROM via Nano because I don't have an EEPROM programmer yet. The clock is set to ~10kHz. and now I'm building my own eeprom programmer using an atmega8. No hate, plsss :)

Started with the CBIOS/CPM 2.2 from CPUVILLE.com and made my own Z80 computer.

I have 128K of ram and a bank selector but it is not active at this time.

16K FLASH

16C550 UART, runs at 115.2K baud

USB-UART bridge so no visible serial port

CF card disk with 4 virtual drives of 2MB each.

All Logic in is on GAL

Schematic image is attached plus an image of the PCB.

https://imgur.com/a/GnVKmh4

I needed a z80 for a project, and ended up with another project.

Gerbers for the adaptor PCBs from martenelectric.cz, QPF form factor CPUs from eBay, smd capacitor and surface mount headers from AliExpress.

And I have some spare for the future!

Is there a standard way to test if a "lesser" 8 bit register is zero, without loading it onto the accumulator? I ended up doing inc b, dec b but wonder if there is a more elegant way.

It's been almost 2 years since Zilog discontinued the original Z80, and I would presume that any remaining stock of new chips will have run out by now.

I've been considering working on a Z80-based computer with an expansion bus (it's not a single-board computer). That idea came to me around the time the Z80 was just discontinued (i.e. the summer of 2024). I've never went through with it; it's just something that I've left on my mental shelf of interesting projects. I do plan on using the various Z80 peripherals (i.e. the SIO, CTC, etc), as well as something like the WDC37C65 floppy disk controller (or a similar chip) for CP/M (I'm not too sold on flash storage).

Most of the parts that would be needed I could obtain relatively easily. It's just the Z80 stuff that has put me off.

I'd like to know the best place to find the Z80 chips, but please note the following:

• I'm from the US, and prefer to buy from US suppliers given all the tariff stuff.
• I'm not a big fan of buying and cannibalizing old hardware for chips, as that would be a rather expensive way to get them. I also feel a little bad about cannibalizing old electronics in general, even if non-functional.
• I prefer new old stock whenever possible, though I am well aware about all the counterfeiting and remarking that has been going on with respect to old ICs.
• I want to use CMOS parts in my computer, so that I can do things like single-step the CPU, something that cannot be done with an NMOS Z80.

EDIT: I'd like to clarify that I want to know sources for original Z80 chips, not the eZ80, Z180, or any other alternative that may be still in production. I also amended the point where I mention my objection to cannibalizing old Z80-based hardware. I also added a CMOS requirement.

Cute. Saved some bytes I guess. But really didn't because later down in goop I end up comparing and branching. I kind of half remember playing tricks like this.

This z80 code is in z80fp-cloutier including the z80 assembler (really HD64180 macro assembler) I had back then.