Arty computers

[M H Stein]

------------Original Message:

Date: Thu, 1 Feb 2007 22:11:24 -0500
From: "Ethan Dicks" <ethan.dicks at gmail.com>

<snip>
Long ago, I did hang a pair of Radio Shack 7-segment LEDs off 
of a PET User Port with some trivial logic to use the 8th bit to select 
digit A vs digit B, then the lower 7 bits of the port went right to the segments.  
A small machine-language routine tapped into the 60Hz clock interrupt
refreshed the digits.  For a modern machine, I'd recommend some sort
of external latch and multiplexer at least, or perhaps a dedicated LED
driver like the ICL7218 (MAX7218?)

(here's one I made a while back with 16 digits from one parallel port
and two driver chips)

http://www.penguincentral.com/retrocomputing/retrogaming/scoreboard.html

-ethan

------------Comment:

For driving 7seg displays or LEDs, I'd recommend an MC14489; it'll directly
drive 5 mux'ed 7 segment displays (hex or pseudo-alpha), straight binary, or 
25 LEDs from a 3 wire DC to 3MHz serial interface. Saves a lot of wiring,
especially if you use multi-digit displays; just the thing for a blinkenlights panel...

mike