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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 19th Nov 2020, 2:04 am   #1
Join Date: Mar 2011
Location: Brotherton, West Yorkshire, UK.
Posts: 89
Default Motorola MC6802 repro (1978)

Another 'lockdown 2020' Retro-Computing project

Back around 1980 I worked in BT's Measurement & Analysis Centre, which was a GEC2050 computer that made test-calls and collated results to improve the telephone service. In each exchange was a TRT302 printer, which contained a 6802 microprocessor board, which we robbed from any faulty printers. I was a Z80 user and this was my first 6800 project, but I hand-wrote a monitor for it and me & pal Steve made development systems from these boards.
40+ years on, I still have that original board, but its forever breaking and I thought I'd make a reliable reproduction using the same hardware and the same monitor program. It has display memory, modify memory, goto program, a serial loader for 'S' records, breakpoint & register display, NMI handling etc... quite complex for a hand-coded project in 1978. The Repro is much smaller and neater but works exactly like the old one.
The noughts-&-crosses game is embarrassingly simple by todays software standards, but its typical of hand-coded, amateur efforts back in the day - of course, its unbeatable, it may be over 40 years old but it never loses!
Getting a micro to play a tune, or to calculate prime numbers was an achievement then, this was all fascinating new territory for the electronics hobbyist.
(PS not sure about 1978 - may have been early 80s)
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Last edited by Phil__G; 19th Nov 2020 at 2:16 am.
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Old 19th Nov 2020, 10:33 pm   #2
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 737
Default Re: Motorola MC6802 repro (1978)

Cool project - never done anything with 6800 series machines although the S68 from ETI is obviously on my radar...

Someone sent me a mail the other day and said that this stuff was so amazing because it was new... perhaps that is why I find it so absorbing as I was aware of it but never got involved at the time.
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