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12672Re: The 1802 Elf and Serial EEPROMs

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  • ajparent1
    Mar 3, 2013
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      --- In cosmacelf@yahoogroups.com, "jdrose_8_bit" <rarecoinbuyer@...> wrote:
      >
      > Hello,
      >
      > I am gathering the parts to build a PE type 1802 Elf for testing the 1861 replacement circuit. Instead of manually toggling the Spaceship code and bitmap into the Elf I would like to burn it into a 256 x 8 bit ROM of some sort.
      >
      > I cannot find any current parallel 256 byte EEPROMs but I have found some serial EEPROMs like the Microchip 24LC02B-E/P. I think I understand how they work. Plus they are very cheap and small.
      >
      > Would it be difficult or possible to use one of these 256 byte 8 pin DIP serial EEPROMs as a ROM for an Elf computer? Or perhaps recommend a 256 byte parallel EEPROM (current or obsolete)?
      >
      > Sorry for the simpleton questions. I am basically new to the hardware side of computers.
      >

      Well several things... In PE style for the Elf, latching the address for more space was one of the simple things to do. so that can be settled.

      As to serial EEproms, yes its doable. The yabut is that you need a program to do the bitbash IO and that would still have to be toggled in and isn't going to be super small. The output line would be Q and the input is one of the unused EF lines. If Q is used for terminal or
      other then a output port could be configured and used.

      I have interfaced those serial eproms to a lot of machines and I lean to the bigger (more bits) parts when I do as once you do the interface code size is a handy thing.

      If you extend the address it's fairly easy to find 8k and larger parallel EEproms.

      Allison
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