"Membership Card" Product Page

Last updated Nov 25 2019. This is an EARLY general product description of the "COSMAC 1802 Membership Card", from its first few years of production.Read the "Membership Card" Home page for current information and to order. Edited by Herb Johnson, (c) Herb Johnson, except for content written by Lee Hart and others. Photos are of the Rev A version, minor changes from current versions.

[rev A] [rev A] The 1802 "Membership Card" set of RCA 1802 CPU card and front panel. A classic minimalist design, programmed at the binary level; with an ultra-low power CMOS CPU from the Space Age. A handful of logic is all that's needed. With a CMOS RAM or EPROM, the CPU board can run on milliamps at 5 volts. The Membership Card Kit is two cards which form a compact stack and fit inside an Altoids can! A third card is optional as an attractive front cover.

The CPU card has the RCA 1802 CMOS processor, RAM chip, and CMOS logic chips. CPU clock is adjustable with a trimpot. This board drives the 30-pin connector to the front panel card, or other I/O cards, as a taller stack.

The front panel card has the switches and LED's to program and operate the CPU card. Through the Molex connector, it attaches to the CPU board, and is easily removed to free the CPU for another board or a cable. A supercapacitor provides RAM power backup when seperating the cards.

The COSMAC ELF was an early 1802 lights-and-switches microcomputer, designed by RCA engineers led by Joseph Weisbecker in 1976, and published in Popular Electronics. Generations of ELF designs were produced and built in the subsequent decades. Lee Hart's 1802 Membership Card is an invitation into that community of ELF owners. First produced in 2009, it was only 1802 computing kit available for several years. . The designer, Lee Hart, explains why he designed the Membership Card in these linked notes.

[rev A] [rev A]

The prototype was first distributed in 2009 as Revision A, and distributed months later as Rev B. The Membership Card is offered as a board set, and optional silkscreened PC cover card, or as a full kit of parts & boards - all supported on a version-specific Web page with links to manual, schematic, and revisions. Testing and operating the Membership Card with the front panel is described in this linked document. Here's an instruction sheet on operation of the Membership Card.

The Membership Card Home page has the links to discussions, developments, documents and construction history. There's several years of development leading to the Membership Card, and links to previous and current revisions. There's also links to ELF and 1802 Web sites, including historic uses of the 1802 micorprocessor - first available in 1976 from RCA.

All those and more Web pages, provide links to test programs to toggle in, software to download, hardware suggestions, and links to more resources. Lee Hart constructed a graphic of how the "elves" run the 1802; and compact operating notes and an 1802 instruction set summary.

Technical Description

This is an EARLY general technical description of the first series of "COSMAC 1802 Membership Cards". Read the "Membership Card" Home page to order and for links to the current support pages.

Membership Card PC boards, shown as CPU at bottom and Front Panel at top; and kit with Altoids can.

[rev B PC boards]

[rev B parts kit]

Membership Card CPU Board features:

  • 1802 microprocessor (option for 1804/5/6 without load mode).
  • 2k-32k memory chip "wide" socket; accepts 2K to 32K RAM or EPROM, addressed at 0000h or 8000H
  • -- narrow RAM socket under wide socket, in Rev G and later
  • supercapacitor to maintain RAM contents with power off or when front-panel removed
  • one 8-bit output port (OUT4, options to change address)
  • one 8-bit input port (INP4, options to change address)
  • option: stack TWO CPU cards for ROM and RAM support, four I/O ports!
  • RC clock with pot (slow for low power, fast for high speed)
  • -- ceramic resonator added in Rev F and later
  • the usual 1802 I/O bits (Q, EF1-EF4, INT, etc.)
  • I/O and power brought out to a 30-pin stacking header to Front Panel card
  • size: 3.5" x 2.125"
  • power: 3-6vdc at milliamps (plus whatever the memory chips require)

    Membership Card Front Panel features:

  • plugs onto the 30-pin connector of the Membership Card
  • provides the Elf front panel interface and DB-25 interface
  • 8 data output LEDs (memory reads and OUT)
  • 8 data input toggle switches (memory writes and INP)
  • 1 Q output LED
  • -- Q and EF3 bit-banged serial port on-board, Rev G and later
  • read/write memory, run/clear, run/load toggle switches
  • 1 input (to EF4) pushbutton, provides manual DMA loading on reset
  • "stand alone" memory read, write, program load, and run operations
  • no PC, external hardware, or any onboard program, are required.
  • size: 3.5" x 2.125"
  • power: microamps, plus a few mA for each active red LED, less for blue

    DB-25 PC parallel port connector on Front Panel:

  • has all I/O and control signals to classic PC parallel port
  • allow operation, upload/download by a classic PC, or simple I/O
  • -- expansion to full 8-bits out, DC power on DB-25

    Membership Card front panel cover

    [rev c cover]

    "A PC board, with holes for the switches and lights and PC parallel port D-connector, silkscreened labels, and a solid sheet of copper on the back. Cut a large rough rectangular hole in the Altoids box, and solder or epoxy this board to the top to provide a neat finished front panel." - Lee Hart

    Power Consumption

    Power consumption of CPU card, running a program with the pot at min/max frequencies, with a Hitachi HM62256P-12 32k byte RAM:

    VCC    ICC at clock(min)    ICC at clock(max)
    ---    ----------------    ----------------
    3v    .12ma    13.5 KHz    .39ma    280 KHz
    4v    .25ma    9.24 KHz    .71ma    350 KHz
    5v    .45ma    7.45 KHz    1.06ma    341 KHz

    The Internet talks about the Membership Card

    July 25 2010: P. Todd Decker's video

    July 28th 2010: "The RCA COSMAC 1802 Membership Card" makezine.com hosted by Gareth Branwyn.

    July 29 2010: "Retro Computer Stuffed Into An Altoids Tin", RetroThing.com post by James Grahame.

    Hackaday.com post by Caleb Kraft.

    The original COSMAC Elf, the 1802 Membership Card, and related 1802 products have been discussed for some time in the Yahoo! cosmacelf discussion group. The Membership card was developed by Lee Hart, during discussions in cosmacelf.

    Read the "Membership Card" Home page to order and for links to the kit support Web page.

    Raves and Rants

    When the 1802 Membership Card was first introduced in 2010, reactions were enthusiastic AND mixed:

    "neato...nerdy..." from those who like projects with lights, switches, and microprocessors at the binary level. "The small form factor, switches, and LEDs make for a very compelling package, and a great teaching tool."

    "still useful...learning tool...CMOS low power" comments from those familar with the 1802 or with modern 8-bit product use. They find the kit a useful way to learn some level of computing far removed from desktop-computer-centric methods used since the 1980's.

    "useless...obsolete...dinosaur...die with the buggy whip" and various remarks showing a lack of interest in "vintage computing" or in 8-bit microprocessors. Lee Hart's work is judged "brilliant...impressive" or "rather stuck in the past", depending on one's point of view (or pointless view). - Herb

    A Web search for "1802 Membership Card" will find many more Web pages, photos, videos of the kit and adaptions. More links are on the Membership Card Home page. - herb

    Contact information:
    Herb Johnson
    New Jersey, USA
    To email @ me, see
    see my home Web page.

    This page and edited content is copyright Herb Johnson (c) 2019 . Contents written by Lee Hart and others is held by those authors. Contact Herb at www.retrotechnology.com, an email address is available on that page..