Call for final Elf99 design input

From: Ethan Dicks <erd_at_infinet.com>
Date: Tue Nov 24 13:47:41 1998

I am cranking along with the capture of the Elf99 design (on OrCAD for DOS,
a 10-year-old program, no less). I wanted to throw out what I have
descided on and ask for suggestions on what is not set in stone.

   The Elf99 will consist of the following:

        o Double-sided PCB, approx 6"x8" (same as the Quest Elf design)

        o CDP1802 processor with discrete CMOS support logic.

        o Socket for 6116/62256 SRAM

        o EPROM enable switch.

        o Circuit to ghost EPROM at $0000 until first address access at $8000

        o Socket for 2764/27256 EPROM.

        o Dual TIL 311 hex latching displays accessible as output port 4
          when in run mode.

        o 8 toggle switches for data entry in load mode, accessible as
          input port 4 when in run mode.

        o Seperate LOAD and RUN switches to permit the user to set the
          computer to "reset", "wait", "load" and "run" modes.

        o A memory protect switch to allow reviewing the contents of
          RAM without changing it.

        o An "Enter" pushbutton to DMA the switch register into RAM when in
          load mode, that can be sensed on EF4 when in run mode.

  Options under consideration:

        o Sockets for two 1822/2101 256x4 SRAMs, the same style used by
          the original Elf.

        o A 1851 programmable input/output port -or- a pair of 4508 latches
          wired as one input and one output port (as in the COSMAC VIP)

        o A 1854 UART

        o A protoyping area of .1" spaced plated-through holes, nominally
          a few inches long by one or two inches wide.

        o Either a dual 4042 address latch or a single 4508 latch. One or
          the other is needed to implement more than 256 bytes of memory.
          This would be optional in a machine built with dual-256x4 SRAMs.

        o A pre-programmed 27256 with a "library" of simple programs
          (Accessible by enabling the ROM switch, setting the program
          number in the switch register, then setting the control switches
          to "run").

Did I miss anything? Any other suggestions? I will not be including space
for an 1861 because I have been entirely unable to locate a source.

Do we still have any interested parties? I have saved the addresses of
all who have initially expressed interest, so I only really need to know if
these features are attracting people or putting them off.

-ethan
Received on Tue Nov 24 1998 - 13:47:41 GMT