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12717Re: [cosmacelf] Re: The 1802 Elf and Serial EEPROMs

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  • Lee Hart
    Mar 8 11:04 AM
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      On 3/8/2013 11:38 AM, jdrose_8_bit wrote:
      > Actually, I do not mind typing in programs. It is toggling in programs that has sorta lost it's novelty. :-)

      Well, that is a simple problem to solve. It just takes a few chips to
      provide a hex keypad for entry and hex LED display for output. The hex
      display was in the original Popular Electronics ELF articles, and
      variations of it were found in the Quest and Netronics ELF as well.

      The keypad circuit can be found in the Quest And Netronics ELF as well.
      it uses a 74C923 keyboard encoder chip.

      > Also, I would like to be able to save any programs that I develop for the PE ELF. Some sort of ROM seems like the simplest and most cost effective way to do it that the Elf can use directly.

      There are all the standard methods, of course. Send or receive data
      serially, using software and the Q/EF4 lines. Or add an EPROM or EEPROM
      programmer and loader; the hardware and software is minimal.

      Another option is simply to battery back up your RAM, so it simply
      retains the data as long as the batteries last. With CMOS, this can be
      many years!

      Finally, one I want to play with but haven't had time. RAMtron makes
      ferroelectric nonvolatile RAM chips. They work the same, and have the
      same pinouts as normal RAM chips, but are *nonvolatile*. No battery
      needed. :-)

      An engineer can do for a nickel what any damn fool can do for a dollar.
      -- Henry Ford
      Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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