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Old Microprocessors, new Microcontrollers and Reverse Poles

Bill Marshall
Engineer, PhD, lecturer, freelance technical writer, blogger & tweeter interested in robots, AI, planetary explorers and all things electronic. STEM ambassador. Designed, built and programmed my first microcomputer in 1976. Still learning, still building, still coding today.


May 15, 2021 10:25

@Bill, do you collect Forth memorabilia?
From my exploits in this area I have an old SmartPACs Forth board serail driven, is that of any interest to you? see attached From the date codes it's early 80's.
I'm not sure how to pm you but raise a support ticket and they will forward my details to discuss.

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May 11, 2021 10:18

Great memories of using Forth on Z8 microcontrollers to control pre-press equipment in the late 80s. I've commented on DS before when Forth has featured in an article and hearing other engineers experiences of those days is always special. I still miss "blowing" compiled code into UVEprom before running on the target hardware. Uploading via USB may be quicker but its just not the same...

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May 10, 2021 10:16

This is brilliant! My first 'proper' coding exercise in assembler for Z80 on ZX Spectrum was to implement Forth! I was only 15 then. I still remember waking up in the middle of the night with realisation why my first add Forth command was doing odd thing around numbers at the edge of 8bit - 256/512/1024, etc... I forgot to use adc for 'high' bytes! ;)

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May 11, 2021 06:57

@clicky Thanks! Ah, the joy of 'bare-metal' programming... That's the trouble with high-level languages: you're isolated from things like the Arithmetic Carry bit. On the other hand, programming at machine level results in a much greater understanding of the hardware. Did you get your Forth working in the end?

April 9, 2021 07:09

Also in the category of Z80 MPUs is the Rabbit 6000 Microprocessor module (RS Stock No. 761-7374) which can operate up to 200 MHz, (at, I think, 2 clocks per instruction) and adds additional instructions and memory management beyond those in the Z80180. It also has a plethora of built-in peripherals.
(I believe the Rabbit 6000 and Zilog's eZ80F91 which clocks at 50MHz are both in the not recommended for new design status, but it is still pretty amazing what a long life the underlying architecture/family has had!)

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April 8, 2021 15:33

I learned Forth back in the early 1980s. Not long after that, I worked on a project adding a GPIB (now known as IEEE-488) interface to a multichannel data analyzer. User needs varied - some would be using the analyzer in automated test environments, and needed the output in raw formats that could achieve the highest throughput across the interface, to keep up with data from multiple channels simultaneously. At other times users needed more human-readable decoded and filtered data output. I ended up borrowing Forth's method of compiling source into a linked list of calls and native code/data. I defined a tiny language for managing the captured data sequencing and formatting the captured data. The user could then use that language to define their desired output and formatting. The interface compiled their request into the series of calls to generate that output. That compiling approach (rather than continually re-interpreting the formatting commands) maximized the throughput capabilities of the analyzer, which was based on an 8-bit 6809 processor.
This is a benefit of learning more than one language (computer or human). They each have their own way of seeing the world, sometimes bringing with them insights into how to better address a problem, even if the solution ends up being implemented in a different language than the insight came from.

May 11, 2021 06:58

@BradLevy Eh, similar here, but at that times on the other side of the iron curtain. Forth was for me the only option to control IEC 625 aka IEEE488 with Czech version of PDP-11, called JPR-12R. Basic language did 6 digit precision, while we needed to measure temperature characteristics of 100 MHz crystals with 1 Hz precision. Forth and application program was loaded from punched tape.

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