Hi Angel, I agree with our opinion on microprocessors vs microcontrollers! The latter are more useful, but the first are much much more fun ;). I suggest you go try with the Z80 - it is really easy to start, and after that you upgrade the project step by step with no problem. After some time you realize that your system is so huge :D

MrCiernioo It's really more fun and more control over the systems, there SDCC C8 CCS etc .. but the ending that I stay with assembler is that I have thus control. I like your channel and I've subscribed to the'll try to mount your plate when you can and be aware of your project. Thanks for all greeting.

Thanks Steve. Video adapter was really a big hardware/software challenge. But most work was put into FAT16 read/write subroutines in Z80 assembler that I implemented later. Other BIOS monitor functions were a lot easier compared to those.

+Satan 2k Hi, thanks for your comment! you`e absolutely right, and I fully agree with your point - It would be more creative to use just basic parts, common for the era. My first attempt on the display board for this project was just like that, but I had to abandon it after encountering a problem I couldn`t solve. The card was disassembled then, parts reused. Later, I found the mistake, but it was too late - I went for a simplier solution with the Atmega just to get things working, and I see it as my personal failure to use modern microcontroller here. Today the project is much advaned, and is running CP/M. New display is being tested, and this time will be more era-correct: Mda/Hercules/CGA 8-bit ISA combo card from PC/XT. I still have plans to make a "proper" VGA or at least composite display from basic logic ICs. However I consider CPLD as a good help here, as it`s a solution simmilar to custom logic arrays chips from that time (Spectrum`s ULA) and can be seen as a larger logic circuit in a smaller package :)

+skil3z ...

haha =)

Hi! At this moment only green VGA signal is connected, red and blue are grounded. If you apply voltage to R or/and B pin, the display colour will change. But it`s still fixed to one color, of course.

AIO inc. Then RadioShack closed down, giving me no parts to actually work with.

AIO inc. What CPU are you using? I'd recommend checking out jameco.com and mouser.com for components. They'll beat RS's prices by a long way anyhow.

The ZiLOG Z80A CPU. DIP40 package, because I already have the socket for that one.

I'm working with the same CPU right now, fun little chip to play with. Check out jameco for your components like I said above. I've really liked their full can oscillators for Z80 clocks

I have a switch for Manual / Automatic clock signals. I'll probably have a video on my channel about the protoboard soon.

Hi, check the blog ciernioo.wordpress.com/ ,and post me a message there, I`ll find them.

Z80 Master Race

Yes, I fully agree. This is where I failed with this project. However, now the computer runs CP/M and is using standard MDA compatible PC Card for ISA slot, looks great and feels better, see ciernioo.wordpress.com/ :) microcontroller based display still sits there and is used for debugging.

I agree

I know. This guy didn't even go out and mine his own copper and silicon, make each transistor via wafer etching and fabricate each microcontroller himself. I think he's even using a monitor he *bought*. What kind of diy video even is this?

@@scotts-tech lol shame him, very funny

Hi! Actually, , the computer happily runs CP/M 2.2 now :) Check my blog at ciernioo.wordpress.com

Hi, sorry unfortunatelly I don't remember, it was one of stock tunes available from youtube film editor.

Hi! I wish I could find some will to do it, laziness still wins here :)

Hi George! In theory it wouldn`t be a big problem - there are dedicated FDD controller chips that would do all the necessary logic, and give a simple interface to uP. However there is a practical problem - it is a real problem nowadays to find a working floppy disk, they are dissapearing rapidly. A much more practical approach is to use IDE interface and Compact Flash cards - easy to use and commonly available. a simple IDE interface could also drive a classic IDE hard drive and connect it to 8-bit micro!

Hi Steve! Keyboard interface to CPU is implemented with 3 chips: 74574 latch, 74245 buffer and 7407 open collector buffers. CPU sends a a byte with only one bit set to 74574, then reads the 74245 buffer to see which collumn and row is shorten (key pressed). 7407 open collector buffers are to protect 74574 outputs from frying because of possible short circuit. It`s kinda classic implementation. Needs a "scanning" procedure to check all collumns and rows for a keypress. Please check my blog ciernioo.wordpress.com/ , section downloads. There is a PDF manual with schematics and listings. Cheers !

Thanks. I took a look at your manual. This provides an excellent overview of the hardware implementation. This leads us on to software. I assume the scanning routine is implement on the Z80. Does the Z80 use some type of internal interrupt mechanism to trigger the scanning code? Or do we have to trigger the scanning routine manually? I really need to read the Z80 manual :-)

I don`t use any interrupt system in my project (except from some demo program for CTC chip). I do scanning manually when I need it - when monitor program expects some user input. Reading a key consist of three stages: We wait in a loop to see if anything shows up on keyboard input port (something different from FFh). If this happens, we do a keyboard scan, to see which line and row of the keyboard is shorten. Then, we decode this information using lookup tables, which gives us ASCII char or control key code. Of course you can use interrupts for some of the work, but it only depends on your system design.

Hi Javier, Thanks! Display connector is for VGA monitor. The project moved a lot forward since I upload this video. Now I`m using real MDA/CGA ISA graphics card instead of a custom AVR-based display board.

Thanks for the answer, I belive to be a 2x16 display connector for debbuging

Because there tend to be less space efficient and also look ugly, a final project could not be called Final if it is on a breadboard :P

also, connections can get loose and cause the system to not work properly

Hi, I wrote it myself, it was great fun actually!

Hi! I have no idea actually, development span for nearly 2 years. My friend made the case for free, some parts were pulled from scrap boards, etc. If I needed something to buy, I just bought it, without looking at costs.

@@MrCiernioo did it run to hundreds or was it not bad?

@@RetroCoderTV It was not that bad actually. The majority of the cost was the PCB boards I think, other components are small and cheap (standard 74LS /HCT series , buttons, goldpin connectors, cables) or not hard to value - used C64 keyboard, old parts like Z80, 8255, 16450, AY, etc - depends where you buy, and if it`s NOS or used. You can always cut some costs on such project, select different parts or look for scrap parts. There were no really hard to get or particulary expensive components.

You realise this is for personal use, right? Also, what monitor do you consider standard, and why? I can't recall any standardisation amongst any of the 8- or 16-bit monitors I every used.

Don`t forget about fun and satisfaction :) People do many things just for fun :D

Hi Issy! Thanks for interest in my project :) You are right: It`s not elegant to use modern MCU in a design like that. For high pixel clock frequency of VGA display that I wanted,( which is allready from different era of 4Mhz Z80 :) ) I had to use something modern that could be able to do the job. It was a hard choice and I`m not particulary happy with it. However, check out my blog - now the computer is mainly running CP/M 2.2 and uses a vintage 8-bit ISA MDA/CGA card from old PC, so it`s more era-accurate now :)

with out 8080 z80 68000 you would not have you're atmega , Knowledge is power.

Or in other words, really lame. however the computer was cool.