Rev H 1802 "Membership Card"

Last updated Jan 16 2016. Edited by Herb Johnson, (c) Herb Johnson, except for content written by Lee Hart and others. Contact Herb at www.retrotechnology.com, an email address is on that page.

This is the Rev H support page. Rev H distribution has ended as of June 2015. The Membership card home Web page will advise you of the current version in distribution of the 1802 Membership Card kits.

Rev H was in distribution as of April 21 2015. In mid-April 2015, some Rev H CPU boards were distributed with Rev G front panel boards. See the Rev G Web page for addditional manuals for that distribution. - Herb Johnson

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. Both photos courtesy of Mark Thomas, who assembled these in June 2014.

Documentation: 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 18 2015.
Here's the link to the Rev H boards layout .PDF dated April 19 2015.
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: the kit comes with red LEDs. Rev H product descriptions and board photos are below.

The Membership card home Web page has links to previous versions, history, testing, hardware and all software - and HOW TO ORDER.

In the news: April 2015 The 1802 Membership Card was shown and sold at the Vintage Computer Festival - East 10.0 in central New Jersey USA, during the April 18th weekend. There were dozens of vintage computing exhibits, many talks, and a 50th anniversary series of PDP-8 exhibits including a newly-restored "straight 8".

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 features and options
Initial testing and programming
Rev H 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 features and options

Small size, common components, assembly manual for hands-on building The front panel and CPU boards stack, and will fit 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.

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 also disconnects the rest of the "stack" from supercap power to the RAM and processor.

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

load/run and data transfer via "parallel port" The front-panel has a DB-25 connector that compliments 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.

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, as documented in the kit manual. The EPROM could contain software drivers or ROM monitor, accessed through PC's RS-232 serial port, or USB port via a serial-to-USB adapter (not included). 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. These features were discussed in more detail on the Rev G support page.

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.

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 detailed description

The Rev H Membership cards consist of a CPU board stacked on a Front Panel board. You can also buy a Cover Board, "a circuit board to cover the switches and lights of the Front Panel card.

1. Membership Card CPU board:

- 1802 microprocessor (option for 1804/5/6 without load mode).
- 2k-32k memory chip .6-inch socket; accepts
6116 2k RAM 6264 8k RAM 62256 32k RAM
2716 2k EPROM 2732 4k EPROM 2764 8k EPROM
27128 16k EPROM 27256 32k EPROM (or equivalents)

- .3-inch RAM DIP socket under .6-inch socket. (Photo on left, courtesy of Mark Thomas, June 2014.)
Accepts Cypress CY7C199 32k X 8 RAM and other .3-inch wide 28-pin RAM

- 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 jumper-select others)
- 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)
- 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 (plus several mA for ROM and RAM memory chips)

2. Membership Card Front Panel:

- plugs onto the 30-pin connector of the Membership Card (assembled Rev G photo by Lee Hart)
- 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,
- serial out active high/low selectable with jumpers; serial in high/low by moving transistor. 
- 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
- no PC, external hardware, or any onboard program, are required for front-panel use.
- size: 3.5" x 2.125"
- power: adds about 3ma for each red LED lit

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)
- allow full front panel operation by "classic" PC (with appropriate software).
- builder can jumper to bring out all 8 bits and bring in +5 on DB-25
- optional: selected pins for hardware serial in and out

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

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 for notes.

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. 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 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.

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 Rev H design incorporates a number of small design changes from Rev G, including a better "driver" for /A15; a diode to improve 1802 reset-on-powerup; and improvements to and documentation changes. 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." Many of these were discussed as fixes or manual changes to Rev G. Look for that discussion on the Rev G support Web page.

Q LED and serial: by Lee Hart.

Lee: "An interesting quirk: Q=1 lights the red LED, and EF3=1 lights the green LED. So you would think that both would light in this loop test, and you'd see yellow. But both LEDs share the same series resistor, and the green LED has a higher forward voltage drop. This means you don't see the green LED; D8 just lights up red. To see green, you can [disconnect your serial external connections and] jumper DB25 pin 20 to power or ground while Q=0."

"When you are feeding in TTL or RS-232 data whose high-state voltage is greater than the Membership Card's supply, then the green does light even if the red is lit."

"You can also enter a trivial program to check EF3, and set Q to the opposite state. Then the LED lights either red or green, depending on the logic level at RXD (DB25 pin 20). This proves that both EF3 and Q and the LED circuits all work." - Lee Hart

Herb: Added to the M/S simple test programs is that "trivial" program to read EF3 and write to Q. It's useful as a "software loopback" to verify your serial hardware and your terminal (program) operation. There's two programs, one inverts the result and one does not. One of them has gotta work...... - Herb

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

late Apr 2015: Rev H in production. Changes to CPU: /A15 FET to transistor or FET-pair to improve rise-time at reduced current. /CLEAR diode, to reset with or without front panel. Jumpers for serial out interface options. 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.