Re: Computing Editorial (please read)

[Michael Joosten <joost@c-lab.de>]

Lee Hart wrote:
> 
> Michael Joosten wrote:

> 
> >>> Some computers really *are* simpler than radios and audio
> >>> amplifiers. In 1978 I built an 1802 "ELF" computer. You can't
> >>> get much simpler, even today!
> 
> >> Flash-based PICs, AVRs, 8051s, and the like, IMHO.  Many of them
> >> don't even require an external resonator, let alone crystal or
> >> oscillator.
> 
> > Right: Take a look at the designs in the Elektor/Elector/Elektuur
> > mags and you'll see.
> 
> You misunderstand. The "Elf" was a complete computer; like an Apple II,
> it included not only the computer itself (CPU, memory, I/O) but also the
> front panel switches and/or keyboard, hex LED display and/or video,
> cassette storage, power supply, expansion slots, etc.

Lee, I hope I did not... While most of the MCU designs for hobbyists
nowadays probably use a serial port to communicate with a small (well,
UltraMon51 is a whopping 8KB!) monitor program, or just use some
parallel PC port to program their internal flash ROMs, it should be
quite trivial to add 6 seven-segment displays (or standard LCD display)
and a small keyboard to arrive at a small standalone system, like the
KIM 1, SDK-85, Microprofessor-1, etc. But the costs are probably often
too high for displays and keys, the development software runs anyhow
mostly on MSDOS at least, so programming in hex isn't fashionable
anymore... 
Yes, that's also how I started, with the Junior from Elektor, a KIM
variant of 1980(6502, 6532, 1KB monitor, 1KB RAM, later with an upgrade
for cassette, serial, addt. 1KB RAM, 2KB Tape Monitor, 2KB Printer
Monitor and a 6522), which I still have (of course!).

To go as 'low' as just having eight switches with some counters to
increment the addresses and the like was ... a bit too early for me,
though such a beast also appeared in Elektor in '77, IIRC, based on
NatSemi's SC/MP. Interesting, but a little too expensive as
birthday/christmas present for a 14 year old.

> 
> PICs, AVRs, 8051's and the like are just chips; there are no complete
> stand-alone computers built with them. About the closest you can get is

Why not - they have the ports, you need some multiplexing with the
external address/data lines, of course.

> something like the BASIC Stamps; a board with one of these CPUs, some
> external memory, a 5v regulator, and connectors for I/O. By the time you
> add a keypad, video, expansion slots, case, etc so it will function as a
> stand-alone programmable computer, your cost and parts count is higher
> than it was for the old "Elf".

Well, a PC has become a commodity device - so it does not really count
in this calculation.

> 
> You probably *could* build a standalone computer with a PIC, AVR, or
> 8051-series micro; but nobody does!

Not sure about PIC, but I'm pretty sure about the others. And I would be
surprised if nobody has already done this with at least the 8051, as
they are older than the other MCUs.
-- 
Michael Joosten, SBS C-LAB, joost@c-lab.de
Fuerstenallee 11, 33094 Paderborn, Germany
Phone: +49 5251 606127, Fax: +49 5251 606065
C-LAB is a cooperation of University Paderborn & SIEMENS