> Why restrict yourself to PC-clone keyboards? May as well just put a
> serial console port on and ...
>Because, as I have traced around countless motherboards of all
>kinds and found this is far easier to cobble up one using keyboard,
>KB controller stolen from old motherboard, than trying to design
>and build a parallel KB or design an i/o and needed codes for
>terminal.
"Designing an I/O and needed codes for a terminal" is dead simple.
Put in a UART, put in TTL to RS232 or 20mA level translators, and you're
done. Want to output a letter in the console? OUT 00H. Want
to input a character? INP 00H.
Come on guys, I'm *not* trying to be difficult. I'm pointing out
that a serial console interface is:
1. Universal. No need to find a particular keyboard design or a
particular monitor scan rate and/or interface.
2. Easy to build - it's just a UART hooked to an I/O port.
3. Easy to program - heck, with many UART's you get interrupt-driven
input and output for free. And no need to write a terminal emulator!
4. Doesn't take up valuable memory space like memory-mapped video.
5. Gives enormous interfacing flexibility. You can hook it to a terminal,
you can hook it to a ASR-33, you can hook it to your PC-clone,
you can put a modem on it and dial into it. You're in fat city.
In brief, it's the option that gives you the most advantages with the
least effort. A no-brainer!
> I have heard horror stories from some who did the parallel
> kbs and they're no longer made. I could be mistaken.
And I think folks who build video generators will run across the same
problem in the future. The computer will easily outlast several generations
of monitors and keyboards, and you want to be able to still use it
in 20 years, don't you? I can use my 24-year-old S-100 boxes with
serial console interfaces just fine today, just as I can use my 30-year
old PDP-8 with anything that has a serial interface, and I expect that
I'll be able to use them 30 years from now. Do you think you'll be able
to buy new VGA (much less EGA) monitors 20 years from now? Heck, the
FCC has an executive order that NTSC television will be gone and
replaced by HDTV in less than a decade - better start buying up
composite-input monitors now while they're still out there!
--
Tim Shoppa Email: shoppa_at_trailing-edge.com
Trailing Edge Technology WWW:
http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
Received on Sun Apr 04 1999 - 21:44:02 BST