When in high school (1974) I built a diode matrix ROM to encode a homemade ASCII keyboard. The keys were strips of masking tape attached to the actuator arms of surplus microswitches. Each key drove a column of the diode matrix and the output rows produced ASCII. Unfortunately, at the time I had nothing to connect the keyboard to. Bob Ammerman RAm Systems ----- Original Message ----- From: "William Chops Westfield" To: "Microcontroller discussion list - Public." Sent: Sunday, February 05, 2006 3:25 AM Subject: Re: [EE] MPROM > On Feb 4, 2006, at 9:13 AM, Peter Onion wrote: > >>> >>> http://petertodd.ca/persist/2006-02-04/mprom_front.jpg >>> http://petertodd.ca/persist/2006-02-04/mprom_back.jpg >> >> Isn't this just a degenerative form of "diode matrix ROM" >> Hardly a new idea I'm afraid ! > > I agree here. Without the requirement of electrical programability, > you've just got a plugboard variant. > > Hmm. I wonder if you can combine a hall sensor with one of those > mechanical/magnetic displays to get the sort of visible programmable > memory you're looking for. A sort of visible core memory, modernized. > It would probably be pretty tough to construct 1000s of bits, though. > (why did you say you wanted thousands of bits? You know that about > 300 bits is sufficient to count the total number of particles in > the universe, and 64 bits of seconds (or even milliseconds) will > count essentially forever...) > > BillW > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist