TTL computing

From: Roger Merchberger <>
Date: Wed Apr 10 15:54:05 2002

Rumor has it that Fred Cisin (XenoSoft) may have mentioned these words:
>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?)

AFAICT, burned fuses should be a logic 0... but I've never worked with
anything less than LSI/MSI, so...

>> 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.

Maybe more with picofuses, but they'd be hard to change [see below]

>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?

If you actually put sockets on the board and insert the fuses into that,
you could simulate an EPROM/Flash[like] part. ;-) It'd take a while to
"erase & re-write", but hey... ;-)

Just my $0.000000000002 [CDN], and it ain't worth that!
Roger "Merch" Merchberger
Roger "Merch" Merchberger   ---   sysadmin, Iceberg Computers
Recycling is good, right???  Ok, so I'll recycle an old .sig.
If at first you don't succeed, nuclear warhead
disarmament should *not* be your first career choice.
Received on Wed Apr 10 2002 - 15:54:05 BST

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