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Old 20th Sep 2018, 8:29 pm   #1
Karen O
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Default Retro computer homebrew: Minimal Z80 computer

This is a Z80 computer that I completed a while ago.

I have only this evening toggled in the example program - echo.asm - and verified that it works.

This must surely be the most minimal of Z80 computers?

One day, I hope to port MS Basic onto it (or maybe one of you will beat me to it!)

Enjoy.
Attached Files
File Type: pdf Orton Z80 computer manual.pdf (377.0 KB, 87 views)
File Type: zip Orton Z80 computer files.zip (3.9 KB, 15 views)
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Old 21st Sep 2018, 12:02 am   #2
Refugee
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Default Re: Retro computer homebrew: Minimal Z80 computer

Are you thinking of adding a floppy drive to it?
I have a box of stuff for the TRS 80 if you are interested.
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Old 21st Sep 2018, 1:06 am   #3
Karen O
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Default Re: Retro computer homebrew: Minimal Z80 computer

That's very kind of you, Refugee, but this computer is more of an exercise in minimalism than anything else.

It has one serial port which in the past you'd run at 110 baud and use an 33 asr teleprinter to communicate. You would save and store your programs using the teletype's paper tape punch/reader.

These days we use a terminal emulation running on a modern PC
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Old 21st Sep 2018, 3:27 am   #4
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Default Re: Retro computer homebrew: Minimal Z80 computer

I offered the TRS80 software before and nothing happened. The computer it was with it long gone.
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Old 24th Sep 2018, 10:15 am   #5
astral highway
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Default Re: Retro computer homebrew: Minimal Z80 computer

Hello Karen,

Just to say Iím loving your batch of ingenious builds and very comprehensive write-ups.

Thereís so much in here, itís incredibly impressive. Iím go My to print out hard copies to study properly as the nights draw in !!

Thanks again !!
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Old 24th Sep 2018, 10:33 am   #6
Karen O
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Default Re: Retro computer homebrew: Minimal Z80 computer

You're very kind, Al.

You'll find the implementation of the serial port a bit nutty, but it works!

I plan one day to turn the 'echo' program into a boot loader, which can then load in a 'checksum boot loader' over the serial link, which can then load in MS Basic. Just like the good ol' days!

Even though I run the LEDs at only 100uA, they are still a bit too bright and dazzling. A testament to the efficiency of modern LEDs?

Enjoy!
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Old 24th Sep 2018, 1:10 pm   #7
dominicbeesley
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Default Re: Retro computer homebrew: Minimal Z80 computer

Nice work Karen.

I like the serial port, deviously daft!
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Old 24th Sep 2018, 4:45 pm   #8
paulsherwin
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Default Re: Retro computer homebrew: Minimal Z80 computer

Very impressive work. Nice construction too.
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Old 24th Sep 2018, 6:43 pm   #9
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Default Re: Retro computer homebrew: Minimal Z80 computer

It takes 500k at least these days to do a serial echo programme what with all the library links etc.. I did like Acorn BASIC with inline assembler.
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