Rev J2 1802 Membership Card

[rev I built]

[rev J assembled]


Page last updated Dec 5 2019. This is the support page for the Rev J2 1802 Membership Cards. The Rev J2 CPU was in distribution from Jan 21 2019, to about July 2019. The J2 CPU board is a modification of the Rev J CPU board; the 4093 is replaced with a 74HC132. Rev J Front Panel boards continue in distribution since July 2 2017. The Rev J front panel board has changes from Rev I, as noted on this Web page. The Rev K CPU, in prior distribution, is described on the Rev JK Web page.

This page is only about Rev J2 CPUs and Rev J front-panels. It contains MANY Web links with support and use information; but there's more background about design changes on the Rev I Web page. Links to order and for more information are below.

The photo on the left is of the assembled Rev I CPU board, by Herb Johnson; Rev J2 looks similar and we'll replace the photo soon. The photo on the right is an assembled and stacked Rev J 1802 Membership Card set, by Herb Johnson.

"For those just tuning in, the Membership Card is a reproduction of the original Popular Electronics COSMAC Elf computer, but shrunk to fit in an Altoids tin! It works the same, and runs the same software." - Lee Hart, developer.

Prices, ordering, contact

How to order: Order the Membership Card from the 1802 Membership Card home Web page. The page has links to current and previous 1802 Membership Card version pages. It also has links to 1802 history, testing, hardware, software, and more.


Product and documents
Rev J & J2 features and options
Initial testing and programming
Rev J & J2 detailed description
Engineering Data
Hardware and software and notes about them
Errors and corrections
Chronology of Membership Card products & support Web pages
Prices, ordering, contact

Pages edited by Herb Johnson, (c) 2019 Herb Johnson, except for content created by Lee Hart and others. To report errors on this page, contact Herb at, an email address is on that page. - Herb Johnson

Product and documents

[parts kit] [Rev I front panel]

Documentation, rev J2: The Rev J2 manual is a .PDF file at this link. dated Mar 24 2019.
Here's the Rev J2 schematic dated Feb 16 2018.
Here's the link to the Rev I/J cheat sheet of 2017. Gives the 1802 instruction set, Rev J connections.

On the left is a Rev J kit parts from May 2018. On the right, is an assembled Rev I front panel, by Lee Hart; Rev J and J2 look much the same.

Rev J, J2 features and options

Small size, ordinary components, assembly manual for hands-on building.The kit has small boards and a handful of components, so assembly can be done in hours over days. Only common readily-available electronic parts are used (except the 1802) and are part of the kit. All thru-hole parts, for easy hand assembly. Assembly manual guides construction, part by part, with testing and debug information. Many kits have been built successfully by happy customers.

Compact - fits in an Altoids tin. The front panel and CPU boards stack to fit in an Altoids tin. The front panel cover board (optional) fits over the Altoids lid. It's quite a squeeze to fit them in, and to fit components on the boards. The manual pays attention to these details. Even the ROM sockets are hand-modified if needed, to accomodate components under and above them. Many Membership Card owners are proud of their "computer in an Altoids can".

Runs without a PC. No other computer, external monitor, or even an onboard program, are required for use; just a battery or AC supply. Front-panel hardware runs, halts, loads by toggling switches and observing a LED binary-byte display. You can program in binary - in your hands - anywhere! These are same features as the classic COSMAC ELF; plus RAM, ROM and I/O options as described here. This is early "personal" computing of the 1970's! Oh - and the toggle switches are premium, not cheapies that fail after a few uses.

Low-power voltage-tolerant CMOS processor and chips The 1802 is a pure CMOS microprocessor, which consumes milliamps of current at 5 volts. But it also runs at 4 volts, even lower! Many RAM and ROM chips will also run at lower voltage, but consume more current. A typical 1802 M/S card may consume only TENS of milliamps at 5 volts. Power depends on ROM and RAM access, and selection of RAM and ROM chips. Contact Lee Hart if you want very-low power consumption, or further specifications. Kits as sold have a variety of parts so results per kit and per use will vary.

[parts kit]

Stable, faster clock frequency with ceramic resonator AND variable clock with trimpot. Near the ceramic resonator is the trimpot, a rectangle. Run the 1802 VERY slow, to watch its action and to save power. Or run at full speed of the resonator. With a HC logic gate for the oscillator, selected 1802s may run at several MHz, 10MHz, or faster.

RAM content saved with supercapactor: Seperating the CPU board from the Front Panel, or disconnecing the power connector, will put the CPU board into a "standby state", program halted and RAM contents saved by the supercapacitor. Content saved for hours, sometimes days; convenient for testing programs.

RAM and ROM on one CPU board The kit comes with a .6-inch wide RAM chip. A ROM can be installed instead and a .3-inch wide RAM chip can be installed under the ROM, to support a ROM/RAM based system. The image on the left, shows the Rev H2 assembled in that way, with the ROM out of the socket. A bypass capacitor must also be added. Components and sockets are chosen for a very tight fit! Read the manual to assemble this carefully.

Load/run and data transfer via "parallel port". The front-panel has a DB-25 connector for 8-bit data in and out. The DB-25 arrangment matches the traditional "PC parallel port". Old-school PC's under MS-DOS can run programs in QBASIC to download and run Membership Card programs; the Windows OS limits that capability and modern Windows computers lack the parallel port. So some M/S card owners have built microcontrollers to operate the Membership Card. See this Note about use of the parallel port by old PC's, with links to examples of use of microcontrollers. Rev H, H2 has more ways to set up the DB-25 connector for 8-bit operation.

serial interface operation via EF3 and Q with an RS-232 interface on one connector, a TTL or 3.3V serial interface on another. A two-color LED shows serial activity on Q and EF3. Serial operation requires a ROM or program to support a "software UART" and to interact with the serial user. The TTL connector is also the +5V power connector and can be compatible with some USB-to-serial adapter cables and boards.

Adding a ROM monitor or BASIC: Lee Hart offers a ROM monitor and BASIC, see the support notes below. A simple ROM monitor based on RCA's UT4 is "IDIOT", see the serial notes below.

Serial connections: Parts for a serial connector, IDIOT monitor ROM, and RAM, and specific instructions are provided on that Web page. A more general and technically detailed discussion of the serial interface and operation of a ROM monitor is on this linked Web page. Serial features were discussed in more detail on the Rev I Web page and much earlier on the Rev G support page.

Microcontroller and prototyping: The 1802 M/S Card is a classic 8-bit microcontroller which can operate a variety of analog and digital devices. The front-panel DB-25 connector and the 30-pin common connector provide means to connect to the 1802 CPU board. Additionally, there's a prototype board as an alternative to the front-panel, entirely available for development, predrilled with tenth-inch solderable holes.

Changes from previous versions: Rev J is mosly a layout change from Rev I. Check the Rev I Web page for some recent changes.

How To order

To order: Refer to the Membership Card home page for the current ordering status. An email address and Web link takes you to developer Lee Hart for ordering and contact.

Your initial tests and programs

The kit manual has test programs and debug information. Also, see this document on Testing the 1802 Membership Card with small toggle-in programs. Basic operations of the front panel are described. There's more links about testing and use, under "features" on this Web page. Other links are to testing hardware Web pages and testing software Web pages are on listed on the home Web page. - Herb Johnson

Rev J & J2 detailed description

The Rev J2 and J Membership card set, consists of a Rev J2 CPU board stacked on a Rev J Front Panel board. You can buy the boards, or a kit with boards and parts. And, you can buy a Cover Board, a circuit board to cover the switches and lights of the Front Panel card. There's also a drilled-out Prototype Board to fit the CPU board. These are all sized to fit an Altoids tin box.

[Rev H2 CPU] [edge view]

1. Membership Card Rev J2 CPU board:

Rev J2 CPU board on left. Edge-on assembled I board on right. The J2 CPU with a 74HC132 on the J2, replaces the Rev J's CD4093.

- 1802 microprocessor (option for 1804/5/6 which have no load mode).
- .6-inch 24-pin socket for 2K to 32K byte-wide RAM or ROM
- also .3-inch 24-pin socket under ROM/RAM for narrow SRAM. 
- supercapacitor to maintain RAM contents with power disconnected or /ON asserted
- HI/LO jumper select on board ROM/RAM for high or low 32K address space
- optional +5 volt power input at DB-25 pin 18 w/diode protection (jumper selected)
- Rev H forward, adds diode to /CLEAR for power-on clear
- ceramic resonator for stable clock, and adjustable with trimpot
- the 4093 gate at U4 of Rev J is replaced with a 74HC132 at U4, for faster clocking
- 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 several mA. depends on clock speed and selected ROM and RAM chips

[Rev J front panel]

2. Membership Card Rev J Front Panel:

Rev J front panel bare board on left.

- plugs onto the 30-pin connector of the Membership Card 
- no PC, external hardware, or any onboard program, are required for front-panel use.
- 8 data toggle switches and 3 read/write memory, run/clear, run/load toggles
* switches are premium good-feel, not cheapies that break quickly
- 8 data output LEDs (memory loading or OUT4)
- 1 input and EF4 pushbutton to load front-panel switch data
- provides the Elf front panel interface and "classic PC" DB-25 parallel interface, 
- one 8-bit output port (OUT4 default, or you can jumper-select others)
- output port multiplexed to four DB-25 pins (PC parallel port)
* OR all 8 bits out to eight DB-25 pins (jumper selected)
- one 8-bit input port (INP4 default or you can solder-jumper select others)
- serial interface with activity LED, software bit-driven from EF3 and Q.
-  serial receive, transmit connections, support TTL/3.3V, or RS-232 voltages.
- 1 Q output LED
- 8 data input toggle switches (memory writes and INP4)
- size: 3.5" x 2.125"
- power: adds about 1-3ma for each LED lit.
(assembled Rev G photo by Lee Hart)

DB-25 PC parallel port connector on Front Panel:
- has all I/O and control signals to classic PC parallel port (8 bits in, 4 out)
- can control run/halt/load front-panel operations
- jumpers to bring out all 8 bits and bring in +5 on DB-25

6-pin serial/power connector
- Q and EF3 used for bit-bang serial (common use for 1802 ELF computers).
- RX/TX and +5 volts compatible with some USB-to-serial adapters
- adds "idle" signal, could be connected to serial (TTL level) RTS line or a toggle switch.

[panel cover]

3. Membership Card Cover Board:

Cover board on left as part of Rev I built kit. Built by Lee Hart.

The Membership Card Cover Board is a PC board to cover the Altoids lid and mounts on the Front Panel board. The board has holes for the switches and lights, power/serial connector, and DB-25 connector. There's silkscreened labels and a tinned copper shield 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.

4. Membership Card Protoboard:

The Membership Card Protoboard is a PC board for prototyping and development. It mounts on the CPU board instead of, or potentially underneath, the Front Panel board. It's sold seperately from the 1802 M/S Card kit or board set. See this Protoboard Web page for more details.

How to Order

Refer to the Membership Card home page for the current ordering status. An email address and Web link takes you to developer Lee Hart for ordering and contact.

Engineering & Change Data

Refer to previous revision Web pages, for additional changes. The changes below are from Rev J. The Rev K CPU is described on the Rev JK Web page.

Changes from Rev J CPU

Again, the CMOS CD4093 quad NAND gate IC is replaced with a higher-speed 74HC132 quad NAND gate. This HC part provides more current and faster switching of the gate used for the ceramic resonator CPU clock. It may improve timing and switching for use of the other three NAND gates.

Lee Hart noted in Jan 2019: quote

1. Rev.J2 (74HC132) draws a little more power than either rev.K (1802 internal osc) or previous revisions (with 4093 gated osc). Most people won't notice or care. For example, 0.6ma at 4v versus 0.2ma on the earlier revs. It mainly affects how long the supercap can hold up the supply.

2. The oscillator "locks on" to 1.8 MHz with trimpot R1 about 2 turns clockwise from the full-speed end. (The "full speed" end is fully counterclockwise). This is in contrast to [previous revs with a] 4093 oscillator, where the pot was about 1/2 to 1 turn clockwise from the end.

3. Rev.J2 (74HC132) oscillates at 1.81 MHz. The 4093 typically oscillated at 1.79 MHz. Either works; Chuck's MCSMP20 monitor still runs at 9600 baud and less.

4. The minimum oscillator frequency moved down a bit; 15-17 KHz for rev.J2, versus 20-24 KHz for earlier revs [with a trimpot]. - Lee Hart

P4 connector, standby and low power notes

Discussion of the P4 connector, by Lee Hart and Herb Johnson, early June 2018. This applies to Rev I and Rev J. Also see the Rev I Engineering notes about the P4 connector.

If you're using TTL serial (or *no* serial), then unplugging P4 lets the /ON signal float high. This stops the clock, resets the 1802, disables the LEDs, and puts everything in "standby" mode. The standard kit comes with older "slow" all-CMOS parts, so power consumption is essentially zero in standby, and the supercapacitor will maintain memory for days.

If you upgrade memory with modern "fast" cache RAMs or faster non-CMOS EPROMs, power consumption will be higher. The RS-232 interface in use, will also increase supercap power consumption. So the supercapacitor may only hold RAM memory contents for hours instead of days.

Some (not all!) CMOS EPROMS with "C" in the model name, are really low power. Slower usually equals lower power. For instance, National 27C256Q 450nsec is low-power. Two "real" CMOS 300-mil RAMs I've identified are Hitachi HM62256BLSP and Sony CXK58257ASP. See this Web page for tests of various 300-mil RAMs and some further discussion.

Low-power tests, June 3 2018, Lee Hart:

1802mc rev.J with National NMC27C256Q EPROM, Hitachi HM62256BLSP 0.3" RAM. Start with supercap charged to 5.30v (what my RS-232 dongle supplies), both tests.

1. Unplug Front Panel from CPU board. After 48 hours, supercap at 1.41v. Plugged Front Panel back in, and the BASIC program I left in memory was still intact and ran.

2. Unplug P4 and DB25 connectors. After 48 hours, supercap at 1.30v. Plugging P4 and DB25 back in, and BASIC program was still intact. - Lee Hart

Errors and corrections

Inverting /EF3 serial input: If you need to invert the serial TTL input on the Rev I or J card, here's a means described by Al Williams. He provided this description, in his notes about use of the Spare Time Gizmo's version of the "ELF2K" ROM monitor and utility. "The solution I used, was to clip R2 off the circuit board completely. Then I wired the left pad of R2 (which connects to P4) to the banded end of D13. This uses Q5 as an inverter. This is equivalent to jumpering [the TTL serial input pin] to pin 20 of the DB25 connector." - Al Williams, July 2017

Hardware and software and notes about them

This Web site has dozens of Web pages about hardware, software, operation and upgrades and debugging of the Membership Card. Please, please look at the Home Page of the 1802 Membership Card for links to those notes. Links are on my hardware note Web page and software note Web page.

Summer 2018: Here's operation of the Rev J M/S card with BASIC 3 and an FTDI-chipped USB serial adapter. Tiny BASIC and the IDIOT ROM monitor were also operated with the FTDI-chipped adapter. Some details and history of BASIC 3 and USB serial adapters are below.

2018: Lee Hart and Chuck Yakym provide a BASIC, Tiny BASIC, and ROM monitor, as binary images you can download to burn into a PROM. See Lee's 1802 M/S card sales page, look under under "BASIC for the 1802". Choose the "Rev J" version for your rev J CPU board. Details are in the ZIP files and on his site. There may be in-development versions on the cosmacelf Yahoo Web site in the "files" section, "Basic 3" folder by Chuck "the-eagle". again, choose "Rev J".

June 2017: Many people use a USB to serial adapter to operate the 1802 Membership Card serial port. Over time, it's been discovered that these adapters introduce hardware buffering of characters sent and recieved. This buffering interferes with timing delays caused by 1802 software, and delays deliberately added by "terminal" programs on the PC in use. Here's a Tech Note which is from discussion of these issues, taken from the cosmacelf Yahoo discussion group. - Herb Johnson

Jan 2017: Lee Hart says "So far, I have tested [the 1802 Membership Card] with the following ROM monitor programs:
- Herb Johnson's IDIOT monitor
Chuck Yakym's monitor + Tiny BASIC at cosmacelf Yahoo [see notes above]
Spare Time Gizmo's Elf2K EPROM

Check the Rev I Engineering notes for some considerations about serial.

Dec 2015: Lee Hart looks at some TTL to USB and DB-9 RS-232 to USB adapters. Here's what he has to say. Further notes about the art of bit-serial on the 1802 M/S card is on this how-to Web page.

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.

To order: Refer to the Membership Card home page for the current ordering status. An email address and Web link takes you to developer Lee Hart for ordering and contact.

Recent History of 1802 Membership Card production.

The 1802 Membership card has had many design changes, to improve operation, provide more user options, or to correct problems. Review previous version's support Web pages for discussions of those changes, or for guidance to use the current version. Consider buying a new-version CPU or front-panel card versus modifying your version. There's often links to notes about such "mods" on the version-pages.

Jan 20 2019: Rev J2 CPU board with Rev J front panel in distribution. This is the Web page for Rev J2 CPU support.

Aug 1 2018: Rev JK as Rev K CPU boards with Rev J front-panels. were in production and distribution. See the JK Web page for details.

July 1 2017: Rev J CPU and Front-panel boards are in production. Some Rev I CPU boards are still being shipped; there's no notible changes for Rev J CPU boards. A transistor was added to the Rev J Front-Panel board for the Q LED. See the Rev J Web page for details. Rev J CPU was retired in Jan 2019.

April 2017: Rev I CPU in production. No obvious changes from H2. Some problems of use were found, see the Rev I page for details.

Feb 1 2017: Rev I Front Panel in production, now with a power/serial connector. The H2 CPU was still in distribution. Some problems of use were found, see the Rev I page for details.

July 2016: Rev H2 Front Panel in production with Rev H2 CPU. A 3.3K resistor R2 was added in series with the RS-232 input; as a change to Rev H.

June 2015: Rev H2 CPU in production with Rev H F/P. The Rev H CPU /A15 address inverter NPN transistor Q1 replaced with 5LN01SP N-channel MOSFET and 5LP01SP P-channel MOSFET to produce the /A15 signal (chip-select for memory at 32-64k). Rev H2 CPU also has a normal 4-pin header for [HI/LO] memory address selection, located on the top of the board.

Check the 1802 M/S Card home page, for links to ALL previous version Web pages. Further details of production and change history are on a history of production Web page.

40 years ago as of 2018, Lee produced an 1802 single board computer called BASYS. Look at the BASYS manual for hardware interface suggestions for the Membership Card.

How to Order

Refer to the Membership Card home page for the current ordering status. An email address and Web link takes you to developer Lee Hart for ordering and contact.

This page and edited content is copyright Herb Johnson (c) 2019. Contact Herb at, an email address is available on that page..