Why the 1802 "Membership Card"?

Lee Hart responds to Hack-A-Day comments about the Membership Card

See the features of the Membership Card on this linked Web page.

One of the Membership Card kit builders posted about their kit on "hack-a-day" back in August 2010, at this Web link. Comments posted to the site pose a number of questions, which were addressed by Lee Hart in his own post there. A comprehensive history of the Membership card is available from the Membership card Home page. - Herb Johnson

I'm the idiot that designed this thing. :-) Why? Many of the comments [posted] provide clues!

To really learn something, you need to begin with the basics. Start at the bottom of the ladder, and work your way up. Master each step, them move up to the next.

But today's computers have basically sawed off all the bottom rungs of the ladder. Those that learned "way back when" understand how computers really work, and they can build and improve them further. But those starting off today look at computers as an appliance (or worse, as "magic"). They don't really have a clue how it works. They depend on someone else to design it, build it, and program it for them.

This leads to hideously inefficient systems. They think that millions of transistors and megabytes of code are needed to do even simple tasks.

But the vast majority of microcomputer applications are tiny little gadgets, like a pocket calculator for example. If Windows and a Pentium were required to make one, there would *be* no pocket calculators! There would be no way to "climb the ladder" to invent them, perfect them, and make them affordable.

The idea of the Membership Card is to show how small and simple a computer can really be. You really *can* build it yourself, from scratch. No surface mount, no custom parts, no proprietary code.

And, you don't need any expensive programming hardware or megabyte compilers. Yes, there are 1802 C compilers; but there are also Tiny BASICs and FORTHs that run with 1/1000th of the resources.

1802 machine language seems odd in light of today's super-complex CPUs; but this machine languge is refreshingly simple. It is Turing-complete; it can do anything that any other computer can do. Basically, it has 16 16-bit registers that can be used for anything; program counters, stack pointers, DMA registers, general purpose storage, etc.

No stack pointer? Hah! You can have *ten* stack pointers if you like. No CALL instruction? Baloney; you write what amounts to microcode to create one. If you want CALL to push the PC and also save three other registers on the stack, then you can! The 1802 makes you *think* about what you want your instructions to do.

Hardware wise, the Membership Card has the same sort of bit/byte input and output ports as a BASIC Stamp, Arduino, or any other micro. I'm using mine to make small robots; the stepper motors connect directly to the output port, and the input sensors connect directly to the inputs. I'm using the Q output and EF4 input for a serial port to a PC.

Another feature of this older technology is low power consumption. The Membership card *runs* on 3v at 1ma. There's a jumper to disable the LEDs, since one LED takes 10 times more power than the whole computer. Or, you can unplug the front panel once you've loaded your program (it's no longer needed) and use the Membership Card by itself.

It takes no great genius to bury a problem with brute force. In constast, hacking is all about finding clever ways to do more with less. "Running light without overbyte" as Dr. Dobbs used to say. The 1802 and Elf computers amply demonstrate this principle!

Lee Hart

Contact information:
Herb Johnson
New Jersey, USA
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This page and edited content is copyright Herb Johnson (c) 2010. Contents written by Lee Hart, are copyright Lee Hart (c) 2010. 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..