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Re: [cosmacelf] Re: membership card

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  • Lee Hart
    ... Agreed. So, what is a good size? Playing-card sized? 3 x5 card sized? What sorts of standard common boxes come to mind? ... Well, one of the things I am
    Message 1 of 116 , Feb 3, 2005
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      rileym65 wrote:
      > Just to put my .02 into the conversation, I think a clearer, easier
      > circuit design is far preferable to small size.

      Agreed. So, what is a "good" size? Playing-card sized? 3"x5" card sized?
      What sorts of standard common boxes come to mind?

      > I could really see for tiny sizes if you are using them as embedded
      > controllers

      Well, one of the things I am interested in are "beam" robots; tiny
      light-powered autonomous robots. While there are dozens of BASIC
      Stamp-like microcontrollers, none of them are within orders of magnitude
      of being as low-powered as the 1802.

      > when talking about something a beginner can put together and use,
      > embedded controllers are just not part of the equation. Better to
      > design a board specefically to that task, in which case all you
      > would need is the cpu, ram, rom, 8-bit latch and i/o connector.
      > That could be done in really small space for those who are after
      > an embedded controler.

      Hmm... how about this then?

      Suppose the "system" consisted of TWO boards; an "application" board
      with the CPU, memory, and I/O -- and a "development" board that has the
      front panel switches, displays, etc.

      This doubles your overall PCB area without making the final package much
      bigger (only thicker). Parts are spread out more, so each board is
      easier to build and layout.

      The application board has:
      - 1802, crystal oscillator, and power-on-reset
      - two bytewide RAM/ROM sockets
      - 8-bit input port
      - 8-bit output port
      - RS-232 port (bit-banger using Q and EF4)

      The development board has:
      - 1802, adjustable RC oscillator
      - Elf toggle switch front panel (8 Data, Load, Run, Protect, In)
      - Elf hex display (or 8 individual LEDs)
      - 256 bytes RAM

      Here's the tricky part. Each of these boards is a fully operational
      stand-alone 1802 computer by itself. But, you can plug them together to
      make a more powerful system.

      I suggest using the 1802 socket itself as the bus connector that
      interconnects the boards. I did this at TMSI for the "Proteus" and it
      was very handy. Each board has a 40-pin IC socket with ~0.5" long pins.
      The 1802 itself plugs into the top of this socket.

      Additional boards are "stacked", with the long pins of the 1802 socket
      of one plugging into the 1802 socket of the next. There is only one
      1802, which goes in the top socket.

      Let's say we have an application board that we need to debug. Build the
      development board with its toggle switches and LED displays on the
      "back". Plug it onto the long pins of the application board, and you
      have a 2-board stack. It has all the I/O and memory of both boards. The
      front panel can examine and load programs, to help figure out what is
      going on.

      How does that sound?
      --
      "The two most common elements in the universe
      are hydrogen and stupidity." -- Harlan Ellison
      --
      Lee A. Hart 814 8th Ave N Sartell MN 56377 leeahart_at_earthlink.net
    • ajparent1
      ... Lee, they run the gamut from cmos parts in the few mils range to around 100ma for the older nmos designs. I have some Alliance CMOS parts pulled from a 486
      Message 116 of 116 , Feb 27, 2005
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        --- In cosmacelf@yahoogroups.com, Lee Hart <leeahart@e...> wrote:
        > One more thought. Can someone who has any of the skinny-DIP 28-pin
        > thru-hole 32k RAMs actually plug one into a breadboard and see how much
        > power they really take? If we can find one that is reasonably
        > inexpensive and available, we could use it on the MEMBER card to save a
        > chip.

        Lee, they run the gamut from cmos parts in the few mils range to
        around 100ma for the older nmos designs. I have some Alliance CMOS
        parts pulled from a 486 cache and they run about 12ma when supporting
        a z80/4mhz. Their drain is cycle time dependent for the cmos. I've
        looked and the general xx256 parts are still fairly easy to find and
        cheap. Do watch for the parts that are semi-static where the address
        lines are latched by CE/. Their power drain is very low but CE/ must
        be asserted for every access.

        Allison
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