"Membership Card" Hardware

Last updated Mar 17 2024. Edited by Herb Johnson, (c) Herb Johnson 2024 , except for exerpts of content written by Lee Hart and others.

This page references hardware for or about Lee Hart's COSMAC 1802 "Membership Card". Here's a link to the home Web page for the "Membership Card" That page links to 1802MC history, development, current status, and links to other documents. There's a link there to the Web page to buy the current available version of the Membership Card kit, and a link on how to order it. There's other Web pages on this site, which reference hardware, as described & linked below.

Hardware notes and references at this site

See the Membership Card home page for the current version (or for your version) of the Membership card for schematics and manuals. This page references hardware notes and content. First, here's the fundamental notes about operating the Card, repairing it, and connecting it to a computer:

How to operate the Membership card, and test programs.
Diagnose a broken Membership Card and build a logic probe
Constuction hint to fit into Altoids tin
The IDIOT ROM monitor, is useful for diagnostics.

Lee Hart created in Feb 2012, a graphic of how the "elves" run the 1802. Lee also wrote some Membership Card operating notes and an 1802 instruction set summary. These can be printed and stored in the Altoid case. Here's the 2017 operating guide PDF version.

The Rev G and later Membership Cards, support both wide ROM or RAM (600 mils) and narrow ROM (300 mils). Here's mods to add 300-mil wide ROM instead of RAM.

Look at our software Web page, for information about any associated hardware supported by the software described.

Today's computers use USB; some don't have serial for legacy devices. Rev G and later versions since 2014 provides a serial interface. Here's a general note about the issues with setting up a serial port and software to use it. Look at most-recent versions of the Membership Card, for discussions and hints about use of USB. On this linked Web page, is discussion form 2017 about various USB to TTL adapters. Here's a Web page on operation of the Rev J M/S card with BASIC 3 and an FTDI-chipped USB serial adapter.

In June 2014, David Kriest assembled a Rev G CPU card as a stop-motion video. See the video on Youtube as "MC Revg" by "Corecoder" for June 13 2014.

In Jan-Feb 2014, Herb Johnson assembled a rev F Membership Card kit, and debugged a stacked ROM and RAM, and an external serial interface. Check those notes for examples of assembly and mods.

For earlier versions without serial support or ROM and RAM, there's notes below about adding an external serial interface or adding a ROM. A kit with RAM, ROM and connectors may be available, or you can make your own. And for loading the M/S card without a ROM to operate a serial port, here's notes on small, simple toggle-in serial loaders.

The 1802 Membership Card is a direct descendant of the COSMAC ELF of 1976, which preceeded almost all personal computers. Lee Hart's variation wires-in the "PC parallel port" to operate and load the M/S card. Here's a note on using the Membership card with a PC parallel port.

Hardware notes on this site:

The OUT instruction and the Membership card
a single-step circuit for the Membership Card.
RCA's 1802 single-step (courtesy of Mark Moulding)
A description of RUN operation after separating the M/S card set
Tech Note about use of the parallel port by old PC's in QuickBASIC.

Low power:
Tests of .3-wide narrow RAM for current consumption
Operate the Membership Card from serial-port power only!
Low power operation of the Membership Card
Low power, solar-cell, operation of the M/S card
Some older Engineering notes about voltage and power

high speed:
Production information about 1802's
pulled 1802's are remarked and resold
1802's at higher speeds and voltages
various M/S card speed tests, power consumption

component details:
Tech Note on speed of CD4013 gate and RAM access, hardware fixes
Tech Note about an undocumented state of the 1802's state lines (LOAD, CLEAR).
Tech Note about transistors with internal resistors, used on the M/S card.

assembly, options, upgrades:
Lee Hart's alarm clock front panel
Some notes and comments about Membership card upgrades
Rev G and up: mods to add 300-mil wide ROM instead of RAM
Notes about assembling and modifying a Rev F CPU kit and boards
Tech Note on adding a ROM to Rev F and earlier M/S cards.
Here's a Tech Note about stacking two CPU boards, to double-up RAM and I/O.
Add a ceramic resonator clock circuit, and stacking ROM and RAM, for Rev C and earlier.
general audio data cassette methods
QUEST Super ELF, ELF II Cassette tape support
COSMAC VIP cassette tape support
Read a ROM on a board connected to the DB-25 interface

Serial and USB:
The Rev J M/S card with BASIC 3 and an FTDI-chipped USB serial adapter.
describes serial interfaces and monitor ROM products for earlier versions.
Serial interface circuit for pre-Rev-G 1802 Membership Cards
Various USB to TTL adapters.
A kit with RAM, ROM and serial connectors, for test and use.
parallel to serial (or USB) loader hardware & software

1802 Membership Card under control

A number of M/S Card owners has shown us their "builds". And, many owners have connected external controllers, or a PC's parallel port, to the Membership card. Others have used their Membership Card as a controller. Look for them on our "builds" Web page.

The M/S card software page, includes links about microcontrollers (like the Arduino and Raspberry Pi) connected to the DB-25 of the 1802 M/S Card.

Old-skool COSMAC development, prototype and "hobby" systems

Get some ideas for how-to-use, from these previous COSMAC ELF-like systems and their documents.

A 1980's 1802 card called BASYS is documented on this linked page. Docs include simple ways to connect motors, relays, other devices.

Microboard Computer Development System with UT61 ROM monitor and BASIC 3 in ROM. I have the binary dump of the ROM; sources by disassembly. This system was built in 1982, and it's a good example of cassette-based development tools of the late 1970's.

Gary Camp's 1977 BSEE project to build an 1802 based thermometer.

RCA's UT5 ROM monitor as part of a CDP18S021 calculator terminal to operate a simple 1802 system.

The RCA Studio II video gaming system is not exactly a "development system", but it's a COSMAC computer. HEre's a Web page that looks inside the Studio II and discusses mods for modern use.

RCA developed a number of prototype COSMAC computers. Some of RCA's early microcomputers are held by museums and private collectors. Joe Weisbecker retained a collection of his early COSMAC work and documentation on prototype COSMAC computers. Those were eventually distributed to the Hagley Library and the Sarnoff Collection. In 2017-18 I assisted the Sarnoff Collection's efforts to digitize their collection of over 100 audio-cassette program tapes from Joseph Weisbecker's mid-1970' COSMAC archives. The tapes held by the Hagley Library were previously digitized by the Hagley. By late 2018, both were converted back to binaries and run under emulation. Read the amazing details of that effort, and access the results, on this linked Web page.

Other companies and groups developed COSMAC systems. In the course of the RCA COSMAC work, I and others reviewed a number of "COSMAC ELF" systems for their cassette formats. Here's a Web page that describes cassettes for data use and links to pages describing many COSMAC ELF cassette schemes.

Other Web sites and other COSMAC resources

Lots of 1802 hardware, from the original ELF to the 1802 Membership Card, are discussed or documented on the groups.io cosmacelf discussion group. Previously it was hosted (closed in 2019) at Yahoo! Groups as cosmacelf. You must be a member of the discussion group, to access files in that group. The corresponding Web site is cosmacelf.com. Dave Ruske operates and/or moderates all these.

At the groups.io cosmacelf Web site, there's a "Files" area, where many COSMAC owners and particularly 1802 M/S Card owners have provided software and hardware projects. Also look at the "publications" section, for newsletters supporting a number of COSMAC "ELF" systems - docs, news, new hardware and software for them. Also described, are a number of Arduino hardware "loaders" which upload and download files to the 1802 M/S Card. Some are stand-alone, some work with a Windows or Linux personal computer. Some can be hand-built, others are based on PC boards as designed; board files and how-to's may be included in the file-folders at the group. Some projects might also be hosted on the user's Web site.

RCA developed the COSMAC microprocesor in the early 1970's: see notes about the earliest 1801 and 1802 versions. But 30 years ago, Lee developed an 1802 single board computer called BASYS. Look at the BASYS manual for hardware interface suggestions for the Membership Card.

See the Membership Card development page for years of discussion about the present Membership Card design, and the philosophy behind it.

Mike Riley developed various Elf computers, and Elf/OS, in the early 2000's. Take a look at his software and hardware; he's still at work.

My Web page on 1802 software, references other Web sites with COSMAC resources both hardware and software.

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

This page and edited content is copyright Herb Johnson (c) 2024. Contact Herb at www.retrotechnology.com, an email address is available on that page..