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Old 12th May 2019, 11:47 pm   #81
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 4,778
Default Re: MK14 programming interface - MK2

I didn't realise the diagram for MK14man's version was available anywhere - I confess I have not been to his site for a while because he seemed to have gone completely off-grid for a number of years - but maybe the details were always there and I just missed them. I don't seem to be able to compete with your (by now legendary) data mining ability.

Although it's good that the programmer could work with the MK14man design after all, that design is so flexible in terms of how the address decoding is done that it ought to be quite possible to reserve an address range as PROM, map some of the non-volatile memory into that range and provide the machine with built-in serial download routines, if indeed that is not already the case. Or, the existing cassette handling routines and jump calculator could of course be replaced with serial download code.

For original machines I considered it essential that the method used should not require any modification at all to the hardware / firmware or consume any RAM or hardware resources not already used by the monitor, so that was why I ended up doing it the way I did.

It was an accidental bonus that it turned out to be possible to upload code at much higher speed than I had expected - I had thought the OS's key debounce delay would limit the upload speed far more than it does.
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