Grey wrote: Wed Jun 23, 2021 4:31 pm
But there were also phones based on the Z80 CPU with indicators and automatic caller ID aka AON.
Hmmm... interesting article. I should have moved to Russia since designing Z80 based-systems (along with its associated interfacing UART chips and so on) was my 'special' expertise back in the mid-80s. Z80 was great processor. I still have some of the demo Z80 assembler programs I used training students in such programming, but though I created such programs, as an electronics engineer the part of the work I enjoyed best was the address decoding, main system design, plus the electronic hardware interface designs so the resulting Z80-cored boards could input/output to the outside world.
One of the very simple programs I created back then was for 3D rotation of a wire-framed cube on an oscilloscope plus it wrote the word SCOTLAND on the scope screen at the same time. i.e. a vector graphics demo, which connected to the oscilloscope from the output port of the Z80 system via a 3-bit Digital to Analog Convertor (which was nothing but 3 resistors in binary weighted value...).
I still remember the program details and actually recoded it later in high level languages like BBC BASIC, and C for the non-Z80 type systems I was working with later. For Z80 program I simple stored all the vector end-point values in tables and used indirect Z80 Load commands to output them via a loop into the rudimentary DAC.
It was really a simple animation, worked out cube by cube and then the coordinates put in the table (i.e. didn't use auto-calculation via any complex maths transformations).
Just found something similar someone has done on an Arduino on youtube video; pity they don't give the code they used:
https://www.youtube.com/watch?v=7LnsF_tOu4s
Mine was better because of the SCOTLAND!!! (And definitely did not require a complex 12bit DAC). Yeah, that was after I first moved to New Zealand, so annoying my students with my extreme pro-Scotland sentiments - I also had to reduce my use of scottish slang so the Kiwis could understand me - they were lucky I came from a part of Scotland that didn't employ heavy guttural speach forms in its dialect so all I had to do was slow my speech down a bit and articulate syllables more conciously... Fact is I could not myself understand the Kiwi accent at all unless the student speaking was situated near the front of the class - Scots tend to use long-vowels, Kiwis clip everything short... We say 'cAAAAt', they say 'cit', for Pussy cats, at least it sounds something like 'cit' to me.... Years later, after being back in Scotland for years, I returned to work in NZ, and by that time I had moved into a Computer Department teaching Linux and also Data Comms - Internet protocol, routing and so on; that brought a new linguistics issue: in Scotland we pronounce ROUTING as ROOTING, but like in the USA I think, Kiwis have a different meaning for ROOTING so they used to laugh when I was explaining the processes involved... I forced myself to say ROUTING in Kiwi pronounciation for a while, but sometimes by accident but more often on purpose I would often throw in my own correct Scottish pronunciation ROOTING at appropriate points in the discussion. Truth is that Kiwis are cut off from the world more generally (hence low Covid rates) so they haven't a clue how to speak properly yet they are very insulting about Scottish pronunciations, which is ridiculous since we are the UK's foremost expert in speaking english more generally (everyone knows that).
Used similar technique for most other robotics control type programs (traffic lights simulation, stepper motor, and so on - best thing about it was that the end pseudo code and actual code ended up very well organised and readable - i.e. not spaghetti... It has remained a habit that I still try my best to organise my code in as readable/understandable form as possible, though, particularly when a quick fix here at home, I make as many messy hacks as anyone else 
wrote music for these phones and even made demos. Here is an 
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