Need advice on learning TTL logic stuff. - Page 1
Forum section: electronics / beginners

author: skysurf76
author_rank: Regular Contributor
timestamp: February 26, 2012, 10:55:58 am
content: Not long ago I read about a 7400 series logic design competition onwww.dangerousprototypes.comand it made me want to start messing around with basic logic to make things. I'm an electrical engineering student and really want to attempt to try to come up with some simple stuff on a breadboard using basic logic chips. I really think the experience would be very educational.The problem is that I know so little about the subject that I really don't even have a clue as to where to start. I know what logic operators are, and I have a limited understanding of how they work together to create more complex systems.I've tried doing some research online, but pretty much everything I come across is ancient because the chips are so old. What I really need is someone to point me to perhaps more recent books about the subject, or perhaps some online resource. I've learned from the research I've done that the basic logic technologies have evolved over the years, so I probably need to learn about that, but again, I don't know where to turn. I even tried messing around on the Texas Instruments websites looking at their chips, but I couldn't really figure much out about the chips other than to find if it was in a DIP package or not.So I guess I need suggestions for books, where to buy the chips, and what kind I should get. I think I could probably get going from there. I'm just looking to perhaps come up with a breadboard design to perhaps add some small numbers and light the correct LEDs as outputs, or other projects on that level.Thanks in advance.P.S. Is calling it "TTL logic" correct?

author: McMonster
author_rank: Frequent Contributor
timestamp: February 26, 2012, 11:24:57 am
content: If you know Boole's algebra, minimalization, Karnaugh's maps etc. then you basically know how to use most of the 7400 chips. Look for academic books covering logic circuit's theory. You can buy those everywhere (I've even seen those being sold per kilograms). And get a simulator like Electronics Workbench or Circuit Maker, I think ancient versions of those are free, but still perfectly usable.

author: ejeffrey
author_rank: Super Contributor
timestamp: February 26, 2012, 11:51:56 am
content: The important stuff doesn't change much whether you are talking about the original 7400 series, 4000 CMOS, the new 74F and 74HC/AC chips, or even basic uses of programmable logic like a CPLD. There is nothing wrong with older tutorials, as long as they are good.The most obvious difference in the new logic families is that they are faster. You need more careful attention to layout for high speed design. The most important difference is that many of the more interesting MSI chips are not present. Programmable logic has basically eliminated the need for many of the special purpose logic devices that existed, particularly in the 4000 series.

author: Psi
author_rank: Super Contributor
timestamp: February 26, 2012, 11:56:33 am
content: Karnaugh's maps are quite fun/interesting. If you've never done them you should have a go.They're one of those funny math things that looks like magicYa really need to see someone else solve one to really 'get-it'.YouTube is probably the best bet.

author: TerminalJack505
author_rank: Super Contributor
timestamp: February 26, 2012, 03:10:10 pm
content: Here's an entire video course on the subject.http://nptel.iitm.ac.in/video.php?subjectId=117106086Get a good book on the subject, read it and watch that course.Like others have said, don't shy away from the older books on the subject. The fundamentals haven't changed any in the past 30 years. You'll likely save a lot of dough too by buying a used book on the subject.Once you understand everything in that course you will find the 74xx chips a breeze.Once you get comfortable with building circuits with 74xx series chips you'll probably want to move on to modern technology which is programmable logic devices--CPLDs and FPGAs. Just one CPLD or FPGA chip can replace dozens or even hundreds of discrete 74xx series chips. You'll have to learn a hardware definition language such as Verilog or VHDL to program them, however.

author: Psi
author_rank: Super Contributor
timestamp: February 27, 2012, 02:30:09 am
content: This guy explains it quite well.(and other videos Karnaugh Maps SOP Minim Part 1-4)

author: IanB
author_rank: Super Contributor
timestamp: February 27, 2012, 04:19:40 am
content: Quote from: Psi on February 27, 2012, 02:30:09 amOh. I tried to watch those, but I couldn't stick it out. I was desperately waiting for him to get to the point, but he never did. That was so slow, and so tedious, and the explanation never seemed to arrive. Is there a ViHart version?

author: Psi
author_rank: Super Contributor
timestamp: February 27, 2012, 06:32:34 am
content: It's far easier to watch than the Indian university vid that TerminalJack505 posted, damn the guy in that video sounds boring.But yeah, there are plenty of other youtube vids on the subject and some are straight up problems being solved.The one i posted gives all the background which can be useful if you have no idea about kmaps.

author: IanB
author_rank: Super Contributor
timestamp: February 27, 2012, 06:50:04 am
content: After abandoning those videos I went and read the Wikipedia article. I got the understanding and explanation I was looking for there fairly rapidly.It was really the pacing of those videos that was the issue, and that is an intrinsic problem with the video format. With a book you can read at your own pace, skip ahead if you have got it already, or jump back to refresh a point you missed. With video you are condemned to watch at the pace set by the presenter whether it suits you or not. I think many amateur video producers go too slowly, as if they think that is good teaching style. But it's wrong; they should go as fast as possible. If I don't get a point I can pause to think about it, or skip back as many times as I like to listen again. Going fast is good on video as long as you have pictures and diagrams and you don't miss anything out. Go too slowly on the other hand, and you leave me little choice but impatience or just giving up on you.Thinking back I'm rather sure I was taught about Karnaugh maps and expression simplification many, many years ago during a first year undergraduate fundamentals of EE course. I can see and understand the elegance of the idea now in a way that I could not appreciate back then.

author: IanB
author_rank: Super Contributor
timestamp: February 27, 2012, 07:11:23 am
content: This is the kind of video pacing I like to see:It covers a fairly elementary subject of course, but even if you didn't get it first time through you could rewind and watch over and over until you did. And you'd never get bored.(And then you might realize that sum of products in Boolean algebra is just like multiplication, and that Km's are just a visual multiplication table, and wow...mathematics is amazing!)

author: johnboxall
author_rank: Unknown
timestamp: February 27, 2012, 09:53:52 am
content: Read "Digital Electronics - A Practical Approach" by William Kleitz. Fifth edition is fine. You can get a used copy for about $10 from betterworldbooks.com. There are newer editions that also cover VHDL.

author: skysurf76
author_rank: Regular Contributor
timestamp: February 28, 2012, 11:35:48 pm
content: Thanks a lot for all the advice everyone. I really appreciate it.

author: vk6zgo
author_rank: Super Contributor
timestamp: February 29, 2012, 12:28:46 am
content: Quote from: skysurf76 on February 26, 2012, 10:55:58 amOld books are good--TTL has been around forever!That said,some of the Texas Instruments,Fairchild,& Philips applications books are THAT old,that they predate the "7400" series designations.They still have very useful information,though.The only real differences between the different TTL logic chips & their equivalents in other technologies are in their Electrical characteristics,performance & so on.A NAND gate is a NAND gate,no matter what technology is used.

author: Psi
author_rank: Super Contributor
timestamp: February 29, 2012, 12:52:32 am
content: Quote from: IanB on February 27, 2012, 07:11:23 ami watched the video, but my mind was going so fast by the end of it that the world now seems slow and boring

author: gregariz
author_rank: Frequent Contributor
timestamp: February 29, 2012, 01:14:58 am
content: If you are an EE student, your school should have some 'digital trainers' sitting around in the lab cupboards. These should have some basic digital building blocks on them that you can learn with (usually using TTL chips), and usually an experiment booklet to go along with it. You should go ask if you can borrow one if they are not part of your first year digital classes already.Otherwise if you rummage around the various kit suppliers they will have a digital trainer available to play with.Talking Electronics is one that came to mind. IIRC he used to have a basic electronics course that used to step through the building blocks. Just a quick look pulled up the following trainerhttp://www.talkingelectronics.com/projects/LogicDesigner/LogicDesignerP1.html

author: westfw
author_rank: Super Contributor
timestamp: February 29, 2012, 03:29:44 am
content: See if you can find a copy of Lancaster's "TTL Cookbook", "CMOS Cookbook", and "TV Typewriter Cookbook" (the last is downloadable here:http://www.tinaja.com/ebksamp1.shtml)These are less "theory" books and more about "how to combine common chips into useful projects and sub-projects." In general, building significant circuits out of small scale chips is something of a lost art; your best bet is books and articles from the days when there wasn't much alternative. Here are some (more Lancaster), nicely collected:http://www.tinaja.com/glair01.shtml

author: IanB
author_rank: Super Contributor
timestamp: February 29, 2012, 03:42:16 am
content: Quote from: Psi on February 29, 2012, 12:52:32 amI loved how by complete coincidence that video turned out to be about Karnaugh maps and boolean logic even though you would never have guessed from the title