Fifty Years of Transistor-Transistor Logic | Hacker News Reader

Fifty Years of Transistor-Transistor Logic

embedded.com

98 pointsgumby34 comments

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.

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.

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.

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 :)

Please, please, pretty please, document your building of the laser harp and do a write up. That's a thing that I've always wanted to do since I saw JMJ, it's an absolutely incredible concept and a nice DIY write-up would really make my day.

I had the same inspiration :)

I'll document it when complete and submit to hackaday.com. There have been many dead ends so far so I'll probably just depress myself if I write it up before I'm done :)

My objective is a parts cost of less than £100 and no programming of devices required.

That is pretty awesome! By 'hardware MIDI' I'm guessing you're triggering a shift register which dumps its contents? Do you do after touch effects?

That's basically it yes. Well there's no way to apply aftertouch to a laser harp nor is there velocity so it'll be hard coded velocity (might have a pedal control in future). At the moment it will just sent note on and off down the wire. It does this using three shift registers (74LS165) and some extra bits for start/stop bits.

I've got it sending notes to my Triton so far which is as far as it has got. The harp front end works with one note as I don't have a laser galvanometer at the moment (will build one). I imagine it'll take another 6 months yet at this rate. Plus I keep getting distracted playing with the nice green laser I bought :)

Oh cool, that makes sense. I got a cheap pair of laser galvos off Ebay a while ago (ok long time ago) and built a simple epicycloid generator with them and a Parallax Propeller chip [1]. It was pretty trivial to work with, send it a voltage and poof the galvos moved.

[1] https://www.youtube.com/watch?v=wlc0lzUpPsw

Cool stuff. Much cooler than doing it with a scope and function generators!

I looked at galvos on eBay but I felt like I was cheating. I tried using mirror on a stepper motor shaft initially as a test but the scan rate was abysmal and it was a £3 stepper so it vibrated the bearings loose. Ended up widlerising it. I have a pile of DVD drives ready to be recycled though. They have the shafts, bearings, magnets and coils to make a galvo with. Plus some more lasers to play with. Current galvo ideas are based on:

http://elm-chan.org/works/vlp/report_e.html

> 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

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

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.

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.

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

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

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.

CPLD's are the step between discrete logic and FPGAs now. You can look at them as exactly what you describe there. They're a great way to implement things when an FPGA is too power hungry or too expensive.

http://en.wikipedia.org/wiki/Complex_programmable_logic_devi...

You must have later PDP-8's, the early ones were DTL, Diode Transistor Logic.

Yes, technically I've got three (8/E, 8/F, 8/M) which are all TTL, the PDP-5 is DTL however :-)

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.

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.

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

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.

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

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...

Thanks. Changed from 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.

That is quite a long TTL!

I also read this and thought, Time To Live.

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

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

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.

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.

Funny I thought of "Time To Live"

same here! haha!

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

Reply on news.ycombinator.com