TTL computing

From: Fred Cisin <cisin_at_xenosoft.com>
Date: Wed Apr 10 12:18:16 2002

On Wed, 10 Apr 2002, Christopher Smith wrote:
> At one point I considered making an "illustrative project" of building
> a pseudo fuse blown PROM out of several inline type fuses -- like are used
> in power supplies, for instance.
> It would be possible to illustrate not only electronically, but visually,
> the way that the ROM works. :) "The black ones are 0s... ;)" (or is that
> a 1?)
> Anything beyond a size of several bytes would be unmanageable, of course.
> I figured you might fit 64 bytes in the size of a VHS tape if you use
> small fuses.

Since the it is for illustration, rather than for significant real usage,
16 bits should be plenty to show how it works.
Glass fuses don't blacken unless you really whack them with a lot of
current, and can sometimes be very hard to even see visually whether they
are blown.
Ceramic fuses, such as what VW used to use would be the easiest to
visually check which ones are blown, but it's hard to find them in smaller
sizes than 8 amps.
Would you be programming in place, or "cheating" and assembly the unit
with fuses that are already blown?
Received on Wed Apr 10 2002 - 12:18:16 BST