
Fifty Years of Transistor-Transistor Logic - gumby
http://www.embedded.com/electronics-blogs/break-points/4431173/TTL-turns-50--more-or-less--in-2014-
======
cicero
One of the best courses I took at Texas A&M in the late 80s was a digital
logic course. We started with boolean algebra and Karnaugh maps. Next we would
draw a schematic for a circuit to implement the logic. After that, we would
get out our TTL Data Book, a required textbook for the course, and find the
parts we needed to build the circuit. There was a room where you could hand
the attendant your parts list, and checkout a breadboard and chips so you
could build your circuit. Finally, we would connect the circuit to a scope in
the lab and make sure it worked. I loved how the course took us from theory to
practical hands-on experience.

~~~
mpyne
I have the same memories of a UNF required computer lab course in 2002 or so.
We were required to learn about flip-flops, various other hardware gates, and
using truth tables and clocks to form hardware logic.

By the end of the course we had to make a 4-bit breadboard CPU that could
handle a couple of operations; a push button acted as the "clock". It was all
very simplistic but at the same time I learned an incredible amount about how
computer hardware works.

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ChuckMcM
I've got a couple of PDP-8 computers and they are all TTL. Its fun to pull out
the three boards that make up the CPU and point out individual things like
registers and instruction decoders, but its also something we'll probably
never do again.

As an intellectual exercise, when Intel announced their 28nm parts a friend
and I tried to estimate if you could get the entire TTL catalog into a single
part. Turns out you should be able to, pretty trivially. We imagined a fun
(but useless) part with 14, 16, or 24 pins that you could drop into a
programmer, pick which chip you wanted and "poof" it would be there (every
chip would have every component in it). At that point an FPGA makes more sense
though.

Some of the 'classic' parts, like NAND gates and inverters are still pretty
useful in teach digital logic concepts, and its fun that folks using Arduinos
and other pin limited devices are using shift registers to get more effective
pins, but the heyday of discrete logic is well and truly past.

~~~
pling
Ive done a fair bit of electronic design over the years (professionally). The
classic parts are still going strong. There are even single gate devices now
in SMD packages!

Outside the world of computing and mainstream consumer tech I expect to see
our friendly TTL devices and op amps etc and even discrete transistors live
another 500 years or so. Some problems are quite cheap and simple to solve
with them and they're well understood.

(I'm building a laser harp completely out of discretes, logic and analogue
components at the moment - not a single microcontroller or CPU in sight. Even
hardware MIDI :)

~~~
paletoy
> The classic parts are still going strong.

But there are very good alternatives for them, be it low cost mcu's,50 cents
fpga's, or even lower-end programmable chips from sillego[1][2]( going down to
$0.2/10K + probably $0.1 more for programming - and that's without
competition). Those are smaller, more reliable(less soldering) and can do
quite complex functions including analog.

So i wouldn't bet on simple gates holding on for 500 years.

[1][http://www.eetimes.com/document.asp?doc_id=1279013](http://www.eetimes.com/document.asp?doc_id=1279013)

[2][http://www.silego.com/buy/index.php?main_page=product_info&p...](http://www.silego.com/buy/index.php?main_page=product_info&products_id=330)

~~~
pling
Low cost MCUs have FLASH which has a finite life. Same with FPGAs which need
to have their brains filled from something.

I worked on a project a few years ago that had a PIC part. They never got the
software working right so we looked at the original spec. The entire software
could be crunched down to 7 gates and a comparator. So we did a rev2 board
with a flip flop and a NAND and a LM358N and there hasn't been a failure
since. To be honest with some bastardising to get hysteresis out if a 555 and
a couple of transistors would have done as well.

The BOM was £0.09 more expensive but the part never failed in production.

The most interesting thing is that PIC part no longer exists so there is no
service option other than replace which costs more down the line.

(This was a watchdog monitor for signalling systems)

Edit: yes I know the 358 isn't a comparator but it was fed just before
saturation to get hysteresis avoiding more parts.

~~~
paletoy
Those are important considerations , but:

You did the design a few years ago, before the silego was a good option.

But for many design , esp in consumer , the silego part would be a good fit
because it would work as same as discrete parts,it's manufacturing life and
reliability(12 years) would be good enough, and it would be better in other
parameters.

And once the consumer market is taken, we might see versions targeted at more
demanding applications. But it's not certain.

~~~
pling
12 years isn't that long. That's less time than XP was around to put it in
perspective...

~~~
paletoy
in consumer markets, do people design for lifetime over 12 years ? Because my
feeling about consumer market that it's mostly crap, reliability wise.

~~~
pling
Rarely. They want it to get through the European statutory warranty and that
is it.

I have an oscilloscope built in 1976 by HP and it's showing no sign of any
problems yet. I'd like to see more stuff like that on the shelves.

------
InclinedPlane
TTL is one of those remarkable achievements that is so blindingly obvious and
elegant that you wonder how everyone got along without it. It makes you wonder
what sort of similar advances will happen in the next few decades which will
make some aspect of the way we do things today look hilariously complicated
and outdated.

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tcas
I still have a copy of a TI TTL Data Book, completely useless these days with
the internet, LVCMOS everywhere, all in one microcontrollers and FPGAs, but
it's still cool to flip through every so often.

~~~
pling
I have the same book and it gets used regularly. Surprisingly not everything
involves gate arrays and microprocessors.

~~~
tcas
I know, completely useless is an exaggeration. I just find it much more
convenient to pull up a searchable/zoomable PDF vs flipping through the book
when I do need to check a specs of a 74/54 series chip.

~~~
pling
My TTL book lives in the bathroom so I sort of agree :)

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pessimizer
This link cuts off the article before the last couple of paragraphs. This is a
better link: [http://www.embedded.com/electronics-blogs/break-
points/44311...](http://www.embedded.com/electronics-blogs/break-
points/4431173/TTL-turns-50--more-or-less--in-2014-)

~~~
dang
Thanks. Changed from
[http://www.eetimes.com/author.asp?doc_id=1322881](http://www.eetimes.com/author.asp?doc_id=1322881).

Edit: We also changed "TTL" to "Transistor-Transistor Logic" since too many
comments were about that.

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arno_v
That is quite a long TTL!

~~~
smutticus
I also read this and thought, Time To Live.

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ecesena
Flagged: the ad is very annoying, plus the title is totally misleading (read
as time to live, as many others)

~~~
dang
If you flag something, please don't also comment that you did.

[http://ycombinator.com/newsguidelines.html](http://ycombinator.com/newsguidelines.html)

The article itself is a good one for HN, as indicated by the fine comments at
the top of this thread.

~~~
ecesena
Thanks, and sorry, I missed that point. My objective was not to shout "hey I
flagged" but propose some changes, that have been done. For what it matters, I
unflagged it now.

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recentdarkness
Funny I thought of "Time To Live"

~~~
recentdarkness
Very funny to be downvoted on a renamed title....

