"Membership Card" Product Page

This is a general product description of the "COSMAC 1802 Membership Card" with links to other pages for details.Read the "Membership Card" Home page for more information and to order. Last updated July 11 2012. 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 an RCA engineer in 1976, and published in Popular Electronics. Generations of ELF designs were produced an built in the subsequent decades. Lee Hart's 1802 Membership Card is an invitation into that community of ELF owners, and the only 1802 kit available during 2009-11. 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; it's at Rev D as of 2012. 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 a general technical description of the "COSMAC 1802 Membership Card". 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 socket; accepts 2K to 32K RAM or EPROM, addressed at 0000h or 8000H
  • 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)
  • the usual 1802 I/O bits (Q, EF1-EF4, INT, etc.)
  • I/O and power brought out to a 30-pin stacking header
  • size: 3.5" x 2.125"
  • power: 3-6vdc at 1ma (plus whatever the memory chip chosen requires)

    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)
  • 1 Q output LED
  • 8 data input toggle switches (memory writes and INP)
  • 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 PC (software in progress)
  • option: expansion to full 8-bits out, DC power on DB-25

    Membership Card front panel cover: available seperately

    [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

    Program retention: I've had it save a program for 10 minutes [powered only by the supercapacitor]. - Lee Hart

    The Internet talks about the Membership Card

    July 25 2010: P. Todd Decker's video and Todd's photos

    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

    "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 "brilliant...impressive" or "rather stuck in the past", depending on what one thinks of people smarter than themselves.

    Public Events

    I showed the Membership card at my sales table at VCF-East 7.0 in May 2011. Vintage Computer Festival - East 7.0 was held May 15-17 at InfoAge in Wall, New Jersey USA. Several people marveled at it. They were familiar with the the COSMAC 1802, the ELF, and the cosmacelf Web site. Many expressed interest in a low-cost, compact kit and product. We sold a few partial kits the year after, at the subsequent VCF-East 8.0 program.

    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) 2012. Contents written by Lee Hart, are copyright Lee Hart (c) 2011. Copyright of other contents beyond brief quotes, is held by those authors. Contact Herb at www.retrotechnology.com, an email address is available on that page..