TTL computing

From: Peter C. Wallace <pcw_at_mesanet.com>
Date: Wed Apr 10 12:56:16 2002

On Wed, 10 Apr 2002, Fred Cisin (XenoSoft) wrote:

> 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?
>
>

Slowblow fuses are self indicating (if a liitle slow to program...)


Peter Wallace
Received on Wed Apr 10 2002 - 12:56:16 BST