I started programming in 1978 (In Assembler) and wanted to know not only how the software worked but how the hardware worked.

Found a great kit using the Z80 and built it and spent many nights with a logic probe and oscilloscope learning digital eletronics. Also devoured the Z80 manual learning the instruction set.

I'm nearly 70 now but remember those days like they were yesterday.

Truly a magnificent CPU

The Z80 was how I learned assembly programming in high school.[0] Was a bit of an unusual choice, but high school students still carry these funky Z80 (or eZ80 now with the color screens) devices every day, so being able to hack on it and have plausible deniability while in class felt great :)

[0] https://github.com/siraben/zkeme80

Z-80 was the processor for my introduction to programming in assembly language on a TRS-80 model I in early 1983. Bill Barden's assembly language books and Hardin Brothers' "The Next Step" column in 80 Micro magazine paved the way.

I wrote a quick post a while back about my Z-80 experiences here:

https://jimlawless.net/blog/posts/z-80/

As the proud owner of a ZX-81 I remember staring at the Z80 instruction reference at the end of the user's manual without the faintest clue of what any of that meant. It took me some while before I managed to wrap my head around how CPUs actually run programs (vs. the high level abstractions like BASIC or other languages).

The article claims: > The Z80 is fully binary compatible with the 8080 instruction set.

It wasn't in regards to the flag register. The parity flag behaved differently for some ops.

And of course it would be possible to write an 8080 program that used undefined ops that would execute in some random way (often just duplicating an existing instruction) while the Z80 repurposed that opcode for something new.

What a milestone. Still my favorite processor, and I have about 10 here at home in various yet to be finished projects (of course).

The heart of the mighty Australian Microbee. I still have the Rodney Zak’s book somewhere although I’ll admit doing anything fancy with assembler back then was a bit beyond me

No mention of the TI-84 calculator? Used by millions of American schoolchildren, programmable in BASIC, and runs on Z80 (B/W models)/eZ80 (color display models) to this day

There is a drop in compatible FOSS clone of Z80 https://github.com/rejunity/z80-open-silicon

The Z80 stopped being manufactured last year unfortunately

My first computer was a soviet clone of a ZX Spectrum, which started it all almost 40 years ago...

This is the CPU that I first learned to code on, first in TI Basic (TI-8[1356] ftw) and then Z80 assembler. Crazy to think that the CPU was "old" when I started, and it's still doing good work in those calculators even 20+ years later.

Two of my favorite Z80 anecdotes.

First, my Father wanted to try to add some peripherals to the original TRS-80 Model 1. So, what he was interested in doing was asserting the BUSREQ pin to tell the Z80 to get ready so that he could have the bus, ideally waiting for the BUSACK signal to know when it was his.

Unfortunately, on the Model 1, when you assert the BUSREQ pin, it is tied directly to the tri-state buffers that handle the address and data bus. So, as soon as you make the request, the Z80 loses all access to its memory and data -- mid cycle. Which, you know, can be Bad. Radio Shack labels this pin TEST and uses it for internal testing. But it was definitely a bit of a disappointment to my Fathers efforts.

The second one is when I learned that the Game Boy Advance has a Z80 built into its chip. The designers drag and dropped a Z80 core (tweaked for GB) just so they could run legacy GB games on it. It just kind of bends your view of the computing world when something as significant as a Z80 can just be shoved into the corner of a die for "just in case" functionality.

Just shows how far we had come at the time.

My son programmed a Z80-based instruction set into a Juno probe sensor. Still kicking.

Off topic: nice, retro website look!

I still remember clearly sitting down to play with the TRS-80 at the local Radio Shack in the 1970s

Unlike anything I had ever experienced, it was life changing, I would bike to the store every day after school

Family couldn't afford the computer but I bought all the books and would read them at home over and over and gawk at all the accessories in the catalogs

Then family surprised me with it as a birthday present with all the relatives paying for it, pretty sure I was the only person in town with one, even the school didn't get one for years

Didn't have any way to save programs, not even the cassette recorder which was too expensive, had to memorize them and retype every time I turned it on

Happy birthday! The Z80 was the first CPU I rode, more luxurious than the subsequent 6502 and 6510. I still have a TI calculator with a low-energy Z80.

Cheers to Rodnay Zaks for "Programming the Z80"!

Back in the day, I studied Z80 assembly to write something about Pokémon red. I didn't realize it was this old