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Sinclair MK14 starting up okay but not accepting keypresses

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    I kind of mistook the manual for being aimed at first time computer owners who would have no idea about any of this stuff and assumed the multiply program was a standalone program to demonstrate what it could do.
    The MK14 manual actually WAS intended to be for people with no previous microprocessor experience - look on the cover, it actually says 'Training Manual' but most people seem to take the view that it was not really very good for that purpose. I only managed to get on with it because, during the agonisingly long delay between ordering my MK14 and actually receiving it I had access to an even more primitive SC/MP system - binary output and input via individual LEDs and switches - so by the time the MK14 did arrive I had some understanding of what was going on and the MK14 felt like a major leap forward with its hex display and keypad.

    I never had a ZX80 so I can't comment on the manual for that but the manuals for the ZX81 and Spectrum were orders of magnitude better, they were actually a joy to read and work through. Of course it helped that by then, they were teaching the reader BASIC rather than machine language.

    With the new rise in popularity of the MK14 due to the availability of replicas, emulators and the occasional lucky find like yours, there could be a case for a group of MK14 veterans to get together and compile / edit the manual which the MK14 should have had. It wouldn't make any money, so it would probably have to be a labour of love.

    There are a limited number of writable addresses on the MK14, the standard memory lies between 0F00 and 0FFF, however 0F00 to 0F11 are used by the monitor for its 'system variables' so the first guaranteed user usable address in standard memory is 0F12, which is why so many programs start at that address,

    If you have the 'optional RAM' (two more 2111s) fitted, you also have RAM at 0B00-0BFF and all 256 bytes of that RAM are available for user use.

    If you have the 8154 I/O RAM chip fitted, you have 128 bytes of RAM at 0880 to 08FF as well.

    Attempting to write to any other address outside these limited ranges will usually give unexpected results.


      Yeah I'm finding the manual to be a bit of a struggle. It's not the worst I've read, but not the best either. Like for example, I went looking for an explanation of what each function key did - but there isn't one. They sort of explain the function on the fly as they plunge you into your first program.

      It's hard to explain but if you read and compare the OSI 300 training manual compared to this one, it's very obvious one was written with the newbie in mind while the other sort of missed the mark.


        To compound matters, the exact way the 'command' keys are used depends on whether you have the original version of the OS (with the ---- -- startup prompt) or the 'new' version of the OS with the '0000 00' prompt. To be honest, I wouldn't waste any time trying to use the original / old OS - I did some testing of the uploaders recently and as part of that process I checked that they worked with an MK14 fitted with the 'old' OS. My own MK14 hasn't had that version fitted since about 1979 and I couldn't believe how slow and clunky it was - for example, the 'new' OS requires three keypresses (data high nibble, data low nibble, MEM) to enter each data byte. The old OS requires five keypresses per data byte entry.

        Broadly, In the 'new' OS, 'Term' changes from address entry mode to data entry mode and 'Abort' changes from data entry mode to address entry mode. Pressing 'Go' will run from the currently displayed address. 'Mem' advances one step through the memory, If you press 'MEM' while in data entry mode, it writes whatever is in the data field to the current memory location, then advances to the next address.

        The actual names / legends on the command key are a spillover from where the 'old' version of the 'SCMPKB' OS was first used, on the American 'National Introkit' (with keypad and display added), so we may never know exactly how and why the command key names were chosen.