24:19 The current limits are the same for all pins so its specified just once under DC Characteristics. It's non-symetrical so different for active high and active low. Iₒₗ is 2.0 mA and Iₒₕ is 1.6mA. If you were using a first generation chip you'd have had problems, but later revisions were built to better specs.

Recently I started a little 8 bit breadboard computer project with the w65c02. Much fun with the literal 0`s and 1`s right on the chips little legs. I also more recently got hold of 6 circuit boards from some communication system, It holds a D780C-1 processor. Turns out I am now the proud father of 6 Z80 oem CPU's. So a search on yt got me here for a Z80 project, Subbed and bookmarked for later.

Hello, good afternoon. Please continue with this project, all my life I wanted to build a microcomputer with the z80. Your way of explaining the subject is excellent. You have one more follower.

It's amazing and brilliant that this was Zilog's first product and it is still in production and sold millions of units. What a great CPU, and still totally relevant today. Ace project as well, can't wait to watch through the progress.

im 25 so i have no nostalgia for this. I like the z80 computers and the cpu because the documentation is fantastic, there are so so many books on the darn thing, its reasonably easy to make a system from, they are cheap and readily available, and because of how old it is, there is a crap ton of software written for it so plenty of example code. This is a fantastic learning tool for any age regardless nostalgia.

Excellent project, thanks for sharing and continue giving life to the Z80

Seriously waiting for the continuation of this series. Great job on the explanation! Regards

Thank you for your excellent contribution. Your explanation is impeccable. I have the Microprofessor Z80 and was wondering how the z80 worked. With your input I have more clarity on this issue. Continue with your project, surely it will be very useful to us. I am one of your new enthusiastic followers.

Just found this. Outstanding explanations. I'm going to build all of this so I can follow along. Thank you!

I just started breadboarding this. I got some C compiled and burned onto an EEPROM but I will have to make my own Z88DK config. After I started connecting it to the Z80 I decided to move the processor to another breadboard and create a bus, putting all of the control, address, and data pins in order. My clock is only 1MHz, so I think it should still work. Then it was early morning so I decided to pick it up another day.

Not useless, not low spec. As a embedded microcontroller, its still very useful, and fast. Just inconvenient, in comparison with modern ucontrollers, with everything onboard.

Fabulous and fascinating. At just the right level!

Thanks for sharing your knowledge Steve.

Great video and excellent way to present, I will watch the rest for sure.

Great video, looking forward to seeing more at some stage.

very interesting stuff, awaiting more...

Cheers Steve, really well explained. My first computer too. Looking forward to part two.

same nostalgia and same dream to build my own computer

Wow. Now I can build my own Z-80 :) Thanks

Just found this series. It looks interesting so I'll follow it for at least an episode or two. Maybe longer. It looks like you're going to be using bank switching. Multitasking? That would be a challenge but an interesting one. I had an idea of building a multitasking / multiuser system which has memory protection to prevent one user's program from intruding on memory intended for a different program. For example, only an instruction executed from the ROM switch memory banks and if a program running elsewhere attempts to do so, the signal is blocked and goes nowhere. This would force running programs to "request" a bank switch when needed and the OS can ensure the request is valid before granting it. Directly jumping to a ROM routine would also be disabled. The running program would need to use a RST call in order to send a request to the OS. Incidentally, it seems that most or all Z80 CPUs will actually access up to 64K I/O ports. This is done by using the IN A,(C) and OUT (C),A instructions. It seems that these instructions actually output the entire BC register pair onto the address bus during the instruction execution, which means you have access to heaps more I/O ports. If you really wanted to, you could even use some of these I/O locations as slow RAM for accessing data. This is undocumented so it might not work on all Z80 CPUs, but it's worth trying to see if your CPU works that way.

I have seen briefly this video in the past but this time I watched it through and I was absolutely enthalled. I believe that the initial standard chip speeds were 2.5MHz and 4MHz and I always found the Z80 to be an understandable chip. Its instruction set and fuction is the same as the Intel-8080 but that require a couple of support chips corrected with the Intel-8085. Somewhere I have all of the chips for a Z80 SBC and a perforated board that I was going to assemble it on. Maybe it is in the loft.

Great video. I started my own series on the Z80 not too long ago.

Nice video. One quick note when you're manually doing the output. Whatever you output is going to be on the same bus as those DIP switches, which some are forced HIGH when the switches are closed. Hopefully no data bus pins were damaged.

This series is amazing and your project is really beautiful, compliments. One question, is possible to have schematics of this project? Thanks in advance

The second inverter on the clock generator is to buffer the clock signal so that things that are using the clock don't load it down.

my first computer was a TRS80, 4K of thundering power expandable to 16K.

Thank you so much.

I might try this project.

Legal!! 😃 Obrigado por compartilhar seu conhecimento do z80!! Eu também quero montar um z80 no protoboard!!

Very well done!

I beg to differ on this with you. I say the main reason for building this is what you will learn from doing it. Keep in mind that the Z-80 is hardly a gutless wonder.

Очень интересно. Спасибо большое :)

Added a like 😊

very interesting and fun.

Nice video.

Going to try this Steve. A question. In Ben Esser's series on the 6502 he talks about not using the early 6502 models because they had dynamic registers that needed to be constantly refreshed by the clock like dynamic memory, meaning slow or single step clocks would cause the processors register contents to disappear. I have what looks like quite an old crusty Z80, just wondering if i might hit the same problem. You don't appear to. Any ideas?

Poderia informar a relação de materiais usados nesta montagem?

Hello! I tried out the circuit, and it works perfectly with automatic clock. However, manual clock does not work as it should in my case: no problem if I press the clock button continuously at a steady pace. But if I stop pushing it, after - let’s say - 1 or 2 seconds all the yellow and blue LEDs turn on. So I can’t really pause the execution. I checked the clock signal with an oscilloscope, and it looks ok. If I stop pressing the button, there is no clock signal. But even in absence of a clock signal, all the LEDs (except halt) will light up after a few seconds.

I was running 1991 to 1996. Now I am walking.

hi, I have a Zilog Z80 like yours, in cmos, but it behaves anomalously, I made the connections like yours, pullup resistors on the reset-busrq-wait-int and nmi pins, I generate a clock with the blink sketch of arduino (for my convenience at the moment). 4 LEDs with resistance on the negative for the address bus A0-A1-A2-A3 and finally I put all the pulldown resistors of the data bus, the only difference from your project is that I didn't put the jumper on the positive for the databus. It shows no signs of life, the clock LED flashes, the RD LED is always on and on the m1 it never activates even after pressing the reset for a long time... Do you have any suggestions, maybe I missed something? if it can be useful my model is Z84C0020PEC

wow, more hardcore than altair/imsai ))

Anyone knowing how, where, to get hold of a Z80 assembler to run on a Pc? Once had Cromemcos Rose running on the Z80 assembling code read from first tape, then floppy disc.

for such system thinking to make a hard disk using clock machanism and self made farric oxide coted disk 😁 hows my idea....from many years its in my mind

Is there a way to copy the programming from a Z80 and transfer it to another Z80?

Choosing a "fairly useless low spec machine" is on the USEer. If you have a USE for a low spec machine as a hardware and/or software driven invention/utility device, then the low spec machine is no longer "USELESS". If you want your computer to decide for itself what it will be used for today, then by all means, USE paywalled corporate driven AI pets!!!!

Hello sir do you have schamtic diagram for this project

Hello

So if you aren’t that knowledgeable why are you instructing all of us?