"Membership Card" Product Sheet

Last updated May 17 2011. Edited by Herb Johnson, (c) Herb Johnson, except for content written by Lee Hart and others. Photos are of the Rev A version. Read the "Membership Card" Home page for more information and to order the Rev B.

[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; and a ultra-low power CMOS CPU from the Space Age. With a CMOS RAM or EPROM, the CPU board can run on milliamps at 5 volts.The designer, Lee Hart, explains why he designed the Membership Card in these notes.

The front panel card has the switches and LED's to program and verify the CPU card. Through the Molex connector, it attaches to the CPU and is easily removed to free the CPU for another board or a cable. Testing and operating the Membership Card with the front panel is described in this linked document.

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 in the subsequent decades. Lee Hart's "Membership Card" is an invitation into that community, and the only 1802 kit available in 2011.

[rev A] [rev A] The CPU card with the RCA 1802 CMOS processor, RAM chip, and CMOS logic chips. A handful of logic is all that's needed. A supercapacitor provides power backup when seperating the cards. The 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 Membership Card Kit: The two cards form a compact stack, which fits inside an Altoids can! The Rev B version has PC board socket pins instead of IC sockets, for more clearance. It's offered as a kit of parts, boards, and construction manual as supported on a Rev B Web page. with manual, schematic, and revisions. Other Web pages linked from that page provide test programs to toggle in, software to download, and links to more resources. Finally, there's a Membership Card Home page which links to the history of discussing and developing the product, including the Rev A kit and its construction.

Rev B Technical Description (Aug 2010)

Membership Card CPU Board:

[rev B PC boards]

  • 1802 microprocessor (option for 1804/5/6 without load mode).
  • 2k-32k memory chip socket; accepts 2K to 32K RAM or EPROM
  • supercapacitor to maintain RAM contents with power off
  • one 8-bit output port (OUT4)
  • one 8-bit input port (INP4)
  • RC clock with pot (slow for low power, fast for high speed)
  • the usual 1802 I/O bits (Q, EF1-EF4, INT, etc.)
  • all I/O and power brought out to a 30-pin header
  • size: 3.5" x 2.125"
  • power: 3-6vdc at 1ma (plus whatever the memory chip chosen requires)

    Membership Card Front Panel:

    [rev B parts kit]

  • 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 OUT4 to OUT7)
  • 1 Q output LED
  • 8 data input toggle switches (memory writes and INP4 to INP7)
  • read/write memory, run/clear, run/load toggle switches
  • 1 input and EF4 pushbutton
  • "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: adds about 3ma for each LED lit

    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)

    Here's a link to the schematic as of Nov 2010.
    Here's a cheat sheet to operate the Membership Card.

    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

    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.

    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.

    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.

    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) 2011. 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..