DIY Z80 Retro Computer #5: Boot From CompactFlash Card

In this episode I make the Z80 computer independent from the Arduino. I show how the bootloader works and how to use a 3V Lithium cell to buffer the static RAM chip.
Circuit diagram, sources, CP/M:
github.com/mic...
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[@rockyhill3]

Excellent videos, very clear and to the point. Thank you!

[@vanhetgoor]

I like this computer, it is so complete and so scientific. The fact that all CP/M programmes ever made can be stored on the CompactFlash is quit an achievement.

[@cowasakiElectronics]

This series is brilliant. This is something I have wanted to do myself for a few years!

[@LeonardoPJ]

Very good video, your Z80 computer is looking very nice.
I'm making a bootloader too but with the eeprom, and I had to make a boring circuit to stop the processor for 5ms to record it, using ram like this is very interesting and simple. Good idea.

[@rob_pic]

NIce system, I should really do more with my RC2014 system.

[@jorgenuviola1666]

i wait your next step, i hope this step will make a crt output for the minimal z80, y want to know how to make one

[@edoardomariascardamaglia4325]

Amazing! What if I want to load the bootloader on an EPROM? Does your bootloader and your CP/M support that without huge changes?

[@DoctorVolt]

You can do this. However there is the function "rl$ldr" in BOOT.asm that restores the bootloader from file when CP/M boots up. This cannot write into EPROM of course, so you need to disable it.

[@edoardomariascardamaglia4325]

@@DoctorVolt Perfect, so I have to think about a logic circuit for the chip enable. Thanks

[@sharoyveduchi]

Will it get to the point of connecting to a more modern monitor of any sort? Such as through VGA or S-video? I would like to get to do this myself one day but it would be neat if it wasn't dependent on another computer.

[@DoctorVolt]

There are some terminal-VGA converters available. These are based on a microcontroller and have UART on one side and VGA for Monitor and USB or PS2 for keyboard on the other side. This allows to use the system without any PC. But maybe I will make some basic Video card for this some day.

[@sharoyveduchi]

@@DoctorVolt thank you!

[@LeonardoPJ]

@@DoctorVolt Changing the hardware a little, you can use a TMS9918, it's super compatible with the Z80. I'm putting it on my

[@DoctorVolt]

Interesting Chip, also also not this sucking SMD stuff. However as what I have seen it only supports 40x24 characters in text mode, while CP/M requires 80x24. But maybe cool for some 80s style "Lego" graphics.

[@LeonardoPJ]

@@DoctorVolt Yessss, the cool would be to have a serial monitor. You really like a lego hahahaha

[@yanparasuacurtisao]

How can I conect a vdeo card like with a TMS9918 on this computer? Im building my own and i want to run CPM from a compact flash, can I run it only with 32KB of RAM? Thankyou!

[@DoctorVolt]

I cannot tell, because I haven´t tried yet. Maybe I will make another video about that one day. But what I can already say is that CPM will also run with 32k of RAM.

[@yanparasuacurtisao]

@@DoctorVolt Thankyou! I will wait for your video! Now I'm thinking about edit the bios of the CP/M to run on my computer hardware, I'm noob at this and dont now how to start with it but I will try.

[@zsombor_99]

Come on, connect this homebrew thing to a real CRT computer terminal! 😉

[@DoctorVolt]

I am working on something similar. Let yourself be surprised