Rev H2 1802 "Membership Card"

Last updated Feb 2 2017. Edited by Herb Johnson, (c) Herb Johnson, except for content written by Lee Hart and others. Contact Herb at, an email address is on that page.

Note: Rev H2 CPU + rev H2 front panel were in distribution together since July 15 2016, until Feb 1 2017 when the Rev I CPU began distribution. The Rev H CPU board was distributed until May 2015; the Rev H front panel until July 2016. The Rev H2 front panel is a minor change to Rev H. Rev H2 CPU is a signifigant change to Rev H. This Web page describes features of each revision. - Herb Johnson

[rev G CPU]

[rev G assembled]

This is the support page for the Rev H/H2 Membership Cards. This page contains MANY Web links with more support and use information. "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. The Membership card home Web page has links to previous versions, history, testing, hardware notes and software - and HOW TO ORDER. This page has information specific to the Rev H cards.

The photo on the left is of the assembled Rev G CPU board, less ROM. On the right, is an assembled Rev G. Rev H looks much the same, with some improvements. Both photos courtesy of Mark Thomas, who assembled these in June 2014.

[parts kit] [Rev G complete build]

Documentation, rev H2: The Rev H2 manual is a .PDF file at this link. dated July 15 2016.
Here's the link to the Rev H2 schematic JPEG dated June 10 2016.
The Rev H2 layout is shown in the Rev H2 manual.

Documentation, rev H:The Rev H manual is a .PDF file at this link. dated April 21 2015 w/Apr 18 "Rev HH" schematic.
Here's the link to the Rev H schematic .PDF dated April 2015.
Here's the link to the Rev H boards layout .PDF dated April 19 2015.

More docs: Here's a compact Membership Card and 1802 operating guide PDF dated Feb 18 2014.
The older Rev G Support page discusses changes which became part of Rev H.

On the left is a Rev F kit parts from Jan 2014; the Rev H parts kit looks very much the same. On the right is a custom build of Rev G with blue LED's and a custom serial connector.

How to order: The Membership Card home Web page, has how-to-order links, plus links to previous versions, history, testing, hardware and all software.

Prices, ordering, contact

Refer to the Membership Card home page for the ordering Web link. An email contact address is there for special orders. - Herb Johnson

Index of this Web page

Rev H, H2 features and options
Initial testing and programming
Rev H, H2 detailed description
Order the Membership Card from the home page
Engineering Data
Hardware and software and notes about them
Errors and corrections
Chronology of Membership Card products & support Web pages

Rev H, H2 features and options

Small size, common components, assembly manual for hands-on building. The front panel and CPU boards stack which fits in an Altoids tin. The front panel cover board (optional) fits over the Altoids lid. Only common readily-available electronic parts are used (the 1802 is the hardest part to get). All thru-hole parts, for easy assembly (no surface mount). Assembly manual guides construction part by part, with testing and debug information.

no PC, external hardware, or any onboard program, are required for front-panel use to run, halt, load control by toggling switches, LED byte display. These are same features as the classic COSMAC ELF; plus RAM, ROM and I/O options as described here.

stable clock frequency with ceramic resonator AND variable clock with trimpot This has been a feature since Rev F.

Standby mode, nonvolitile RAM: Seperating the CPU board from the Front Panel will put the CPU board into a "standby state", program halted and RAM contents saved by the supercapacitor. Removing the power connector limits supercap power to the RAM and processor.

RAM and ROM on one CPU board The kit comes with .6-inch wide RAM chip. A ROM can be installed instead and a .3-inch wide RAM chip can be installed under it, to support a ROM/RAM based monitor. A bypass capacitor must also be added. See the Rev H, H2 manual for details.

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.

optional serial interface operation with an RS-232 or TTL serial interface via EF3 and Q. The TXD transmit output, can generate a negative voltage level for improved RS-232 operation. A two-color LED shows serial activity on Q and EF3. The interface can be constructed for inverted or non-inverted serial in and out. All this is documented in the kit manual. Rev H has a 5-pin jumper to configure recieve, a transistor repositioned configure transmit. An EPROM could contain software drivers or ROM monitor, accessed through a PC's RS-232 serial port, or a USB port via a serial-to-USB adapter (not included, details below).

optional ROM monitor and serial connectors: A "kit" with serial connector, IDIOT monitor ROM and RAM and specific instructions, is described on this linked 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. Other monitors or programs can be run from ROM. These features were discussed in more detail on the Rev G support page.

To order

To order: Refer to the Membership Card home page for the current ordering status of the Rev H and H2 kit. An email address and Web link takes you to developer Lee Hart for ordering and contact.

Initial testing and programming

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 H, H2 detailed description

The Rev H and H2 Membership card set, consists of a CPU board stacked on a 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". These are sized to fit an Altoids tin box.

[Rev H CPU] [Rev H2 CPU]

1. Membership Card CPU Rev H & H2 boards:

Rev H image on right, Rev H2 image on left

- 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.  
[edge view] - supercapacitor to maintain RAM contents with power off - 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) - HI/LO jumper select on board ROM/RAM for high or low 32K address space: Rev H, HI/LO solder jumpers on back; Rev H2, jumpers pins on front - /A15 address inverter: Rev H, NPN transistor Q1. Rev H2, a pair of N and P FETs as Q1 and Q2 - Rev H and H2 added a diode for power-on clear. - 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 (replaces R/C in early versions) - clock adjustable 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 (depends on clock speed, several mA for ROM and RAM memory chips)

- (Photo on left, courtesy of Mark Thomas, June 2014.)

[Rev H front panel] [Rev G assembled]

2. Membership Card Rev H / H2 Front Panel:

- plugs onto the 30-pin connector of the Membership Card 
- no PC, external hardware, or any onboard program, are required for front-panel use.
- run, halt, load control by toggling switches, LED byte display
- provides the Elf front panel interface and "classic PC" DB-25 parallel interface, 
- optional serial interface with LED activity, software bit-driven from EF3 and Q.
- see note about H2 revision from rev H
- options to logic-invert serial in and out
- 8 data output LEDs (memory reads and OUT4)
- 1 Q output LED
- 8 data input toggle switches (memory writes and INP4)
- read/write memory, run/clear, run/load toggle switches
- 1 input and EF4 pushbutton to load front-panel switch data
- "stand alone" memory read, write, program load, and run operations
- size: 3.5" x 2.125"
- power: adds about 3ma for each red LED lit, less with other LED's
(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

[panel cover]

3. Membership Card Cover Board:

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, 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.

How to Order

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

Engineering Data

The Rev H and H2 design incorporates a number of small design changes from Rev G, including a better "drivers" for /A15; a diode to improve 1802 reset-on-powerup; improvements to serial setup; and documentation changes. For the H2 CPU design, Lee Hart said April 21st: [The Rev H /A15 address inverter NPN transistor] "Q1 replaced with 5LN01SP N-channel MOSFET. Its pull-up resistor replaced with 5LP01SP P-channel MOSFET. The two of these form a CMOS inverter to produce the /A15 signal (chip-select for memory at 32-64k). Rev H2 also has a normal 4-pin header for [HI/LO] memory address selection, located on the top of the board."

Apr 2015, narrow-RAM bypass capacitor C6, comment by Lee Hart: "If you BUY these capacitors, be sure to get them with X7R dielectric; not Zxx or Yxx series dielectrics. You need a good fast capacitor to properly bypass those dammed-fast 0.3" RAMs. They have really nasty power supply current spikes." The Rev H manual describes the part as "C6: 0.1uF X7R axial lead ceramic capacitor (Mallory P20R104K5; Jameco 536542)". It's "axial", a cylinder with leads at either end.

Dimensions of assembled Rev G, preliminary, Feb 24 2014, Lee Hart: "Though it's very close, the height [of the stacked boards] is a bit too thick to get the Altoids case to close. Not using socket pins for U8 (the .3-inch-wide RAM) would help; maybe enough. I'll have to build one that way and see." - Lee Hart

Rev F & G Power consumption by RAM choice, changes to RAM addressing See the Rev G support page Engineering Notes for details.

CMOS .3-inch RAM: Many 300 mill SRAMs are not CMOS, not low power. Lee Hart, Mar 1 2014: "I discovered Hitachi also made the HM62256 (CMOS 32K x 8 RAM) in a 0.3" wide DIP.. The 62256 is a true CMOS RAM, and so has a low supply current -- essentially zero when static, even if chip-select is held low. It is about 1/10th as fast, and about 1/10th the operating power of the Cypress CY7C199 RAM. The [relevant] Hitachi part number is HM62256ASP, HM62256ALSP, HM62256BSP or HM62256BLSP. A "speed" number follows this, but any speed works in the Membership Card. Suffixes [mean:] A or B is new, P means it is a plastic DIP, S means "skinny" 0.3" wide DIP, L is selected for lower supply current... They are out of production [but may be surplus]."

More hardware notes: Here's a link to some earlier engineering notes about power consumption, program retention, current consumption of LED's by color. There's also more information in the docs for previous versions.

The Rev G and H uses "resistor biased transistors" for the serial interface. A Tech Note about transistors with internal resistors, used on the M/S card serial I/O. Here's the data sheet for the FJN3307 NPN and Here's the data sheet for the FJN4303 PNP

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. Collections of hardware note Web links and software note Web links are on these linked pages.

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 of the Rev H kit. An email address and Web link takes you to developer Lee Hart for ordering and contact.

Errors and corrections

The manuals for the Rev H or Rev H2 have descriptions of parts and functions. The following information also describes them as changes from previous revisions. Owners of previous revisions might consider reworking their cards to incorporate some of these changes if useful and possible. - Herb

June 11 2016, H2 front-panel revision, Lee Hart: [On the front-panel board] I am adding a 3.3k resistor (R2) in series with the RS-232 input. It doesn't affect operation; but limits the [Q5 emitter] current so you see a larger negative voltage (like -9v) when the external RS-232 driver is making the input low. Without this resistor, the negative voltage is more like -1v to -3v (depending on how strong your PC's RS-232 driver is). Since this negative voltage is used by the 1802MC's RS-232 output for its "low" state, the RS-232 serial output was likewise -1v to -3v in the low state. It worked anyway, but RS-232 standards say it should be -5v or lower. [This change updates] the Rev.H Front Panel board to Rev.H2."

For more explanation, Lee Hart: "An RS-232 input is supposed to look like a 3K-7K resistor to ground. Higher doesn't matter, unless it's so high that it affects the max baud rate. Thus I didn't worry about the inverting case (RXD to base of Q5, which has an internal 22k resistor; [emitter to ground]). In the NON-inverting case, RXD goes to the emitter of Q5. The base of Q5 goes to VDD. Suppose RXD is -5v. The 22k internal base resistor then has about 10v across it, so Ibase = 450uA. Q5 has a gain of about 50, so Ic (and thus Ie) tries to be 22ma! RXD can't supply that much, so you wind up with only -1v or so. Hard to explain, but easy to see with a multimeter. "

June 2015: Rev H2 CPU 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). Some of these were previously discussed as fixes or manual changes to Rev G. Look for that discussion on the Rev G support Web page. Rev H2 CPU now has a normal 4-pin header for [HI/LO] memory address selection, located on the top of the board - not underneath as in previous revisions.

Rev H design: April 20 2015: The Rev H design incorporates a number of small design changes from Rev G, Lee Hart says, April 20 2015: "I tweaked a number of things. The changes only removed R15, and added P6 and D15; but they ripple through the parts list, schematic, illustrations of the boards, etc. so lots of things had to change slightly. Note in particular my attempts to improve the assembly instructions for the serial I/O." Rev H has a 5-pin jumper to configure recieve, a transistor repositioned to configure transmit.

Max clock speed for serial operation

Herb Johnson: I've found that maximum speed for the M/S card seems to be "set" in a stable manner, by rotating the trimpot fully counter-clockwise (CCW), until it "clicks" - note that rotational position. Then rotate the trimpot clockwise, "about" half a turn but *no more than one turn*. ( the manual says 3/4 clockwise.) It may not be well-stated, but both the IDIOT monitor and the ELF2K monitor, "want" the clock set to maximum (ceramic resonator labled) speed.

An oscilloscope to monitor the clock at CPU pin 1, shows how the clock speed quickly declines once the trimpot is turned more than "about" one turn from maximum clock speed. But the clock is a little "mushy" at the very maximum CCW setting, and a little more "square" when backed off roughly as described. - Herb

Reverse Chronology of 1802 Membership Card products, support and development

July 2016: Rev H2 Front Panel in production, A 3.3K resistor R2 was added in series with the RS-232 input.

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.

late Apr 2015: Rev H in production. Changes to CPU: /A15 FET Q1 changed to transistor to improve rise-time at reduced current. /CLEAR diode, to reset with or without front panel. Rev H front panel: 5-pin jumper for serial input, to invert or non-invert. Some Rev H CPU boards were sold with Rev G kits.

Feb 2014: Rev G in production. Adds optional narrow RAM to sit under .6-inch wide ROM and optional hardware for serial interface. Fix in Feb-Mar 2015, change Q1 CPU FET to resistor-biased-transistor for improved /A15 signal. Other fixes discussed as manual changes for Rev G owners. See the Rev G support page for discussion.

May 2013: Rev F in production. 1.8 MHz ceramic resonator replaces cap C1 in clock circuit. Here's the Rev F support page.

Earlier design and production by date is now on a history of production Web page.

2005-2009 development history: See the Membership Card development page for years of discussion about the present Membership Card design, and the philosophy behind it.

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.

This page and edited content is copyright Herb Johnson (c) 2017. Contact Herb at, an email address is available on that page..