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Old 7th Apr 2020, 10:48 pm   #338
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 4,079
Default Re: MK14 schematic revisions

To be honest, having experienced the horror of the original early version MK14 keypad which used a large conductive rubber mat rather than dome switches, I don't think I would ever put anything less than real switches on a replica. However there's no denying that the 'Martin' replica with that nice re-manufactured keypad overlay is by far the most authentic looking of the replicas.

Couple of other things - One, I assume (since you did not say otherwise) that the keypad edge connector connection layout is as per original MK14s, and not as per the JM PCB which has a different, (arguably more sensible) layout?

Second thing: Would you mind using the monitor to look at the contents of address 0000, 0200, 0400 and 0600 and let us know whether the contents of 0200, 0400 and 0600 are...

-The same as 0000?
-Different to 0000?

As far as we know the 'Martin' replica is an exact clone of the original issue V PCB. If it is, the 'unwanted' PROM images which are present at 0200, 0400 and 0600 on earlier MK14s should be absent on your machine. If they are absent that's good because it means the way is clear for you to map something else (memory, more I/O, etc) into the address space at 0200-07FF. On earlier issues, the PCB has to be hacked about in order to remove those unwanted PROM images before you can start mapping things into that address range.
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