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Old 20th Dec 2018, 4:02 am   #140
Slothie
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Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 1,287
Default Re: MK14 schematic revisions

Quote:
Originally Posted by SiriusHardware View Post
I remember that the 2114 was different in terms of chip select lines and so on, but I am suggesting - maybe not on your initial V1.1 revision, but on V2.0, that you rearrange it so that it -only- uses 2114s since all of the 256-byte 4-bit types are becoming economically unobtainable.
Thats pretty much what I was thinking... I would end up with 2 versions, one "authentic" and one thats possible to put together from more available components. If was doing that then I'd think about adding a footprint for a 2716 EPROM since its not given that the TESLA proms are going to be around forever...

Quote:
Assuming you are still going to use BPROMs to hold the monitor code then you might consider using a third BPROM as a custom address decoder to generate with one IC the awkward chip enable intervals which would otherwise have to be generated with a 74138 plus more logic. (You may have your Tesla programmer up and running by that time).
My concern other than availability would be that the BPROMs may not be fast enough when its access time is added to that of the RAM and Monitor ROM, but that would be something that would be easy enough to try out, and would make fully expanding the MK14 to 512b prom + 3k RAM possible, and would make many more complex VDU projects feasible (Like MK14 space invaders ??!!)

Anyway, since I now seem to have a decent collection of SC/MPs I don't see why I shouldn't build a number of variants! I'd like to see a small computer with NIBL on it and a very simple display. I do have some 9 digit 14 segment alphanumeric displays somewhere...
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