Demonstration of a Z80 computer with a Memory-mapped Display and a PS-2 Keyboard Interface
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- čas přidán 2. 11. 2020
- This is a demonstration and detailed explanation of a Z80 computer with a memory-mapped composite-video-output display and a PS-2 keyboard interface implemented with TTL ICs. This makes this computer "stand alone" in the sense that it is not dependent on a dumb terminal or PC running a terminal emulation to do console input and output. In addition to demonstrating the computer I go through the schematic, showing how the display and keyboard circuits operate. For more information about this project visit www.cpuville.com/Projects/Stan...
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Thats actually really cool. I built my first z80 "computer" not too long ago. z80, 32k rom, 32k ram, and an 8255 with a buffer chip. got it to blink an led on pin 0 of port A.
Very nice! Thanks for the detailed explanation. 🙂
This is one of the coolest computer project I've seen!!! I'd love to see it in PCB form as a kit, that'll be awesome.
A very clean and distilled implementation!
Donn, your article "Setting up CP/M 2.2 on a New Z80 Computer" available on CPUVille is the best reference on porting CP/M to custom hardware. It helped me in a personal project that runs CP/M on a Esp32 microcontroller. I think I owe you a beer. Thank you!!
Thanks for your comment. I am happy the article helped you.
This is such a nice video! I liked your explanations. It's so good for learning or refreshing / recalling something you knew already! Thank you !
beautiful job
A really interesting way to display video! Thanks for the Info. Hopefully I get one of your kits for Christmas and I get the opportunity to try to test my own display output.
Exactly what I was looking for. Thank you!
Thanks for the explanation!!
That is Super Cool!
New Sub in Case you're Still Rockin It!
Hidin' in Dryden, MI
Fantastic. This circuit to make a video, is same like Sinclair ZX81
Спасибо за видео :) Очень интересно!
hope to get in-touch to ask some questions. I have a RC2014 z80 kit from another maker.
Have questions? Ask me if you need additional info on your project. I designed Z80 based systems starting from 1978.
My Hardware design list from back then:
CPU board with 2 serial & 2 parallel ports, interrupt hardware & RTC
Disk I/O boards for Floppy, Hard Drive, RAM Drive and more
Video I/O boards & complete video terminals
Keyboards - serial & parallel (ASCI)
Intelligent Communication boards for remote mainframe connections
And Much More
I looked into the RC2014 z80 kit and did more research. I finally settled on, and just ordered the SC126 Z180 SBC / Motherboard Kit. It uses a Z180 CPU with a clock speed of 18.4 MHz, making it 4.6 times faster than the classic 4 MHz Z80 CPU. Don't know when I will receive this kit. Basic specifications:
Z180 CPU running at 18.432 MHz
512k byte RAM
512k byte Flash containing RomWBW
512k byte Flash containing SCM
Two asynchronous serial ports
Two 5 volt SPI ports
One 5 volt I2C bus master port
Real-time clock
Voltage supervisor
Three 80-pin expansion sockets
RomWBW is a ROM-based operating system for retro computers. It includes CP/M 2.2 and Z-System and supports a wide range of hardware, including SD cards and Compact Flash cards for storage.
Cost $62.00
see:
www.tindie.com/products/tindiescx/sc126-z180-sbc-motherboard-kit/
Hi Donn. I have one of your boards from a few years ago and I still play with it from time to time. It's running CP/M and I'm programming in Turbo Pascal, trying to recreate some old sports analysis programs I wrote for my Dad about 40 years ago. Turbo Pascal is pretty amazing. Using a combination of source file includes, overlays, shared global variables, and execution chaining, it is totally possible to write useful programs and run them on a 64K Z-80 system.
Anyway, the all-in-one single board computer with video mapped display is exciting. Here's an idea if a full CP/M system is too ambitious ... build a 2-CPU system. Basically take your two boards and glue them together. One system runs the real CP/M system and outputs to a terminal line. The terminal line is hardcoded to connect over to the second computer, which acts as a self-contained VT-100 terminal. Build a simple terminal program into the ROM of the second computer (surely there is some open source code out there somewhere that could be used). Turn it on and whala, a self-contained terminal-based system that doesn't actually need an external terminal, all built using legacy chips (more-or-less). That would be exciting I think.
An lastly, how hard would it be to add support for a parallel printer. Oh that would be so sweet. I just bought a dot matrix printer on EBay. Fun stuff.
Hi Kevin. Thanks for your comments.
A parallel port for a printer would be simple to make. Kind of like the LED output ports on the bus display for the Single-board Z80 computer.
You are right, you could make a separate terminal using a Z80, with a composite video output and a keyboard interface. The Z80 computer with the memory-mapped display has the basic terminal design in it, but you are right you could put it on a separate board. But the terminal would be only a character device, and I wanted to design a system with a memory-mapped display for graphics, so that is what I did with this project.
@@donnstewart706 That's great. You've done really great work. What I have in mind is the ultimate home-made, built from new parts retro computer. Inside it has 2 Z-80 SBCs, one which is headless/serial and one which can act either as a standalone computer or act as the terminal to either the built in SBC or a terminal to external computers (like if you wanted to build a PiDP-11 or an Altair 8800 clone, it would be good for that). A switch on the front controls which mode you boot into. There's also a RaspPI inside the box, because why not. The PI can also act as a terminal, allowing you to ssh into the box and then minicom out to the Z-80 SBCs. At least one of the Z-80s has the full setup with CP/M, 2 external floppy drives (real floppies) and a hard drive or flash rom. The whole thing goes inside a custom-built pizza box (low height) chassis. Building the chassis out of wood is acceptable. Extra bonus points for building the chassis out of sheet metal, aluminum, and/or 3D-printed parts. The chassis has built-in risers so you can slide a keyboard underneath, and sturdy enough for a CRT monitor on top. It's all totally doable. Your boards would cover most of what I described with a little tweaking. Probably the hardest part would be building the chassis. One of the main motivations is to do retro-computing in limited space but still using genuine parts not emulation. I only have a very small work area in my garage, so if I could have an all-in-one neat and tidy compact unit, it would be really nice.
Sorry, a little late to the party. What is the actual CPU speed taking into consideration of the wait states from the video? Is the CPU only running during v-Sync and h-Sync? love your projects and working on my own but I don't have balls to video myself thinking about it plus I'd actually have to finish it. lol Love the work, keep it up. You inspire many including myself.
The CPU is independent of the display. The only times the CPU has to wait is when accessing the video display memory. (Actually, when accessing the 32K chunk of RAM that contains the video display memory. I did it this way to simplify the control logic.) It has to wait until the display is finished with a line, or with a page. However, if the CPU is accessing the other 32K of RAM that does not have the display memory it works at its regular speed.
Can you use a normal these days monitor ?
You can use most modern flat-screen TVs, they usually have a composite video input. But modern computer monitors are usually HDMI or VGA only.