The Bob Ross of micro computer design. Very enjoyable. Thanks much.

this just made me pull out my breadboard and some salvaged z80 cpus. thanks for inspiration for a fun afternoon :D

Thanks for doing this! I was planning a build with my I/O consolidated into an ATmega32A (or similar) but wasn't 100% sure how the interface to it would work. Most projects use ATmega microcontrollers as the main system chip.

Excellent videos! Please more of that!!

Pretty nice! Thanks for this video.

Gracias, Saludos desde Peru. Tank Y, Greatings from Peru

One addition to the question of pullup resistors on the z80 data lines: In Interrupt mode 2, when the CPU reads the vector from the device, D0 *must* be 0. Having a pullup there might cause problems.

G'day, your schematic design style is certainly unique with regards to the use of the bus structure for everything, not one I'd personally use in this form or recommend but when it comes down to it of course as long as it works for you it's cool :-)

Very informative, thanks!

I've never seen anyone use the BUS feature of Eagle like this.. This is really cool and lets the diagram be very understandable.. Thanks!

a little late, but why not a 2x4 latch for memory select? you built one with two other chips.. not that it really matters but it makes it cleaner on the board..

Muito legal!!😃 Obrigado pelo conteúdo! Vou montar um computador com z80 pra mim também!!🖤

Aweome project! Can you add a option to boot from serial in the next episode?

U dont need to replace parts after making any changes to footprint or symbol. Just hit library-> update all

25:00 what you're doing is a *basic way.* the *easiest way* would've been to just use a 1-to-2 decoder. something like the 74LVC1G19 (that one's literally the same logic as you built, but in a nice easy package). MEMRQ->enable, A15->input, A->MEMLO, B->MEMHI, done.

Just realised there's a free edition of Eagle. Play time!

Why not use Z80 Dart or Z80 Sio ?

I pretty much do the same as you but I use a square pad for pin 1 so that if I decide to not silkscreen that part, it is easily identifiable.

The SCCS Interface magazines from the 70s is a good start (and a great read). they were ground zero. google. Emulation on a PC is a good practical beggining. then there are 10-15 USD SBC pcbs out there, an easy off the shelf method for quick results.

Yeah, I imagine it'd take quite a while to design an 8-bit computer if you're starting from pretty much only knowing how to calculate resistance. Cool vid, btw

I am watching this, since i am intterested in the computers. Then i want to repair, an old z80 computer.

Under memory-hitachi there's a generic 62256P memory. I dont know why is under memory-hitachi but its there ;) Also the 74HC parts are under 74xx-eu. Dont know why but 74xx-us only has 74LS.

There is no part 3....

From a usability perspective, eagle looks like a nightmare to use.

I don't mean to be discouraging at all, but I agree with Ingmar M's comment on your use of busses. There are a lot of similarities between how you and I picked up electronics from scratch. I have no formal training. I just have a ton of time to goof around due to becoming disabled in 2014. By no means do you need to change what works for you, and please don't let any criticism influence your decision to create content. From my perspective, the only time I've seen a schematic use busses and labels kinda like this is on an enormous server PCB schematic that had a couple hundred pages. Robert Fedevel went over that one recently in a 3 part upload (so far) about PCB design practices. I highly recommend looking him up on YT (his channel is his name). Almost all of his content is intended for Altium. Personally, I came across some of his uploads but didn't really value them because I thought of them as Altium specific. When I'm given a choice of OSHW/FOSS'y projects I always choose the open option. So by default I've learned KiCAD. I'm especially glad I took the time to learn it now, as the more recent KiCAD 5 release is awesome, and since Autodesk bought Eagle I would have dropped Eagle anyways as I hate the idea of subscription software tools. Open software is forever. No one will ever be able to take that away and it will only improve over time the more people use it. [stepping off soapbox] sry...Anyways.. The tips and tricks that Robert Fedevel shares on his channel really helped me to improve my schematics and layouts. There are also a few uploads from Dave over on the EEVBlog channel where he did timelapse videos of some projects showing how he does schematics and layouts. I saved several of these uploads on a 'PCB Design' playlist on my account (there is one playlist on Fabrication and another for Design). It's all links to other people's stuff and I'm not monetized so I don't care about self promotion. My playlists are intended as a form of personal notes and bookmarks, but I made them public bc these kinds of moderated and indexed references could be helpful for others. The way your using busses here would require me to use software and a 'highlight net' feature to effectively trace the connections. That is a necessity when it comes to enormous schematics but this type of design doesn't flow and I find it very unintuitive. Personally I don't use busses unless it's a really rare circumstance where I have sequential pins with a bus specific function that are routed one to one across multiple devices. If I can clearly route a trace I always try to, and I avoid using labeled nets in favor of dedicated tags("global nets" are dedicated tags as they are called in KiCAD). This creates a physical object on the page that is a bit easier to see and correlate across the page. When my schematic is complete I go back and add the simple "label nets" to any connections that do not have a "global label" on them already so that they are named on the PCB layout side, but I don't use them to make connections. My personal goal is to create schematics that are as easy as possible for others to follow using just the pdf output without the need to use my/other software, or read my notes or description. That's just my goal for these kinds of things. I'm super slow and inefficient though, so I could never ask others to do like I do. I'm simply (overly) openly sharing my perspective and experience because I appreciate when people have shown me things like this more directly. I actually followed Julian Ilett's "blink a Z80" upload yesterday and got one counting in binary on a breadboard for the first time. Now I'm building a little 8 button analogue-ish programmer setup and looking for different ways to latch and buffer it to create up to 16 bits in latching registers along with buffers to display the values on LEDs. I'd even like to have a 7 segment display to show the HEX values of the buttons and registers. Do you have any suggestions on what devices to use? I have some 74LS273's (8 bit D Flip Flop registers) that I salvaged from old equipment, but they are limited to 200uA on the output, so a buffer for LEDs is mandatory. I imagine this is going to be the case with most TTL registers and is probably needed anyway because 200uA (max) on a breadboard and wiring setup doesn't seem very reliable. I have a bunch of CD4050's (non-inverting buffer) anyways. That just adds complexity to what should be a simple prototype. I found a reference to DM9368's on stack exchange. Those are 4 digit binary input/hexadecimal output 7 segment display driver ICs. They aren't dirt cheap but can be had for around $1.50 each in 10× quantity from eBay/AliEx. I've thought about using 74HC245s for registers as those have a tristate system but parts on hand > ordering more. Any suggestions for building such a manual device for testing old MPUs? I'm also doing a 555 oscillator, 5 volt regulator, and using a buffer stage to generate a crystal oscillator circuit for an all around MPU tester board, along with extra pull up/down resistors on headers, and some extra switches, LEDs etc. Is there anything else you wish you had on hand while playing with old 8/16 bit MPUs? -Jake

I don't understand this "reinventing the wheel" when you all could make a better one for something like $2.

Why 2 rams?

a microcontroller? that's not a real z80 computer!! with a hex keyboard with latches and counters you can easily mount a direct ram writer, with the z80 hold in high state for writing