Latches and Flip-Flops 1

Latches and Flip-Flops 1 - The SR Latch

Рет қаралды 1,100,590

Күн бұрын

This is the first in a series of computer science videos about latches and flip-flops. These bi-stable combinations of logic gates form the basis of computer memory, counters, shift registers, and more. In particular, this video covers the set-reset latch, otherwise known as the SR latch. It begins by reviewing the basic building blocks of SR latches, namely NOR gates and NAND gates, then goes on to describe the workings of an ‘active high’ SR latch built using NOR gates, and the workings of an ‘active low’ SR latch built using NAND gates. Truth tables that describe the behaviour of SR latches are also covered, including the invalid combination of inputs that might result in a race condition. Applications of SR latches are mentioned, such as mechanical switch de-bouncing. The videos that follow this one build upon the principles covered here and include the gated SR latch, the gated D latch, edge triggered pulse latches and the master slave D type flip-flop.

Пікірлер: 534

@latedeveloper7836 3 жыл бұрын

1:30 NOR gate and NAND gate explained 2:25 NOR gate and NAND gate can be used to make an S-R latch 2:35 Cross-coupling of 2 NOR gates in an S-R latch 3:17 Starting state of this S-R latch example 3:55 Resetting the latch 4:17 Pulse removed 4:25 Applying another pulse and implications 5:05 Implications of applying a pulse to S 5:27 Truth table 6:15 Truth table after applying a set pulse 6:25 Truth table after removing the set pulse 7:15 Race condition 8:00 Active High S-R Latch Explained 8:41 Truth table for Active High S-R Latch 9:20 Active Low S-R Latch (i.e. built from NAND gates) 9:44 Forbidden state of the S-R latch built from NAND gates 10:00 Summary 10:37 Switch bounce problem 11:37 Examples of applications of an S-R latch

@tensorbundle 4 жыл бұрын

In my 12 years of engineering education, you are first professor who clearly and concisely explained the SR latch operation without causing any confusion. You are a genius. Thank you sooo much

@ComputerScienceLessons 4 жыл бұрын

You flatter me. Thank you. :)KD

@gizmodobaggins7040 3 жыл бұрын

@@ComputerScienceLessons The changing of colours like we are watching a super slow speed playback reallly really helps to understand what is happening, thanks!

@lumerify 9 ай бұрын

12 years of engineering education and you're still learning about SR latch. Oof much?

@andrewwatts1997 3 ай бұрын

Or a failure of education.

@SnoozeDog 7 жыл бұрын

This video better than any other explanation, short to the point

@supermariozaken 7 жыл бұрын

Are you kidding? 12 minutes for something that can be explained in 3

@javerianadeem5556 6 жыл бұрын

Marquis Chan nice

@youngcitybandit 5 жыл бұрын

@@supermariozaken 3 minutes? if anything he covered the topic quite efficiently but it was only long due to him slowly speaking for his viewers.

@johanhendriks 4 жыл бұрын

@@supermariozaken where's your 3 minute explanation? Please share a link

@humanbeing1149 4 жыл бұрын

the game lumber tycoon 2 has these stuff (roblox)

@stevenmcg1986 6 жыл бұрын

I am currently taking a digital fundamentals class for my computer degree and I have been struggling a lot with these chapters that are starting to cover latches and flip flops. I have a difficult time comprehending material simplify by reading out of the text book, and I've tried several videos on KZfaq to help. None of them have worked; they have still been too confusing. Your channel has been a blessing so far. Very easy to understand on how slow you explain the information and the visuals are good. I'm going to continue watching them all and taking notes. Thank you!

@ComputerScienceLessons 6 жыл бұрын

That's great to hear. Thanks for the lovely feedback.

@yuurishibuya4797 4 жыл бұрын

That’s great to hear, shows you have not given up and you are trying to understand, learn by finding different ways. Small tip: You mentioned you had trouble understanding the concept by reading the prescribed text book right, now that you know this topic, go back and read the chapters covering this in the book. This time concentrate on how the author is trying to communicate this information in the book. Why his language constructs are difficult to understand, how you can break it out so that next time you can learn a difficult concept by reading a book written in a convoluted language.

@essennagerry 2 жыл бұрын

@Sundeep Kumar That's also my question... because in the very, very beginning there is no signal from anywhere, so do we regard that all as 0s everywhere? Then we get two 1s after both NOR gates which feed back to each other and their input becomes 0 and 1 for both, which then means their output is two 0s, which means makes their inputs once again all 0s, which makes their outputs two 1s again, etc, etc. Endless loop. Is a flip-flop in such an endless loop eithout any electricity and any input? I really need someone to define the beginning for me, how does it all start. If it starts with the S signal setting it, then all those 0s are valid input, so why aren't they valid before the S signal sets it? That's really confusing to me.

@essennagerry 2 жыл бұрын

@@yuurishibuya4797 That's a good tip! Another tip I would give is to try qnd imagine visually what the author is trying to say with words and try drawing it, maybe even draw it in panels just like the panels of a video explaining it.

@DanilKarlos 5 жыл бұрын

Finally a perfect explanation with a great and easy to understand accent

@realmzakaria 5 жыл бұрын

Thanks god it's not in indian accent lol or I would fail man!

@TheAnnoor 5 жыл бұрын

that's racist

@jszlauko 5 жыл бұрын

No, it's not racist, as he is just saying that the indian accent is very hard to understand, and I agree.

@IchCharacter 4 жыл бұрын

You mean that our hearing is racist or our ability to understand certain accents is racist? I guess it's very racist that we haven't started making every language and culture an obligatory subject in school yet, huh? We can afford the extra decade. I hope you better understand all Scottish and Irish accents perfectly, otherwise you're a total biggot. And God help you if there's any African accent you don't understand flawlessly!

@mimdim925 4 жыл бұрын

Indian english in general is different to british english. i dont speak english as a first language, and british english was the english i had to study, so from a non english speaking background a subset of english i learnt is easier to understand than one with a different set of english. that being said some indian youtubers are very helpful

@D34THM45T3R 5 жыл бұрын

One the clearest most concise videos out there on SR Latches. Much appreciated !

@user-pj9tk4op4w 3 ай бұрын

The question is who's running first the upper nor gate? or the lower nor gate from the previous state in order to go to the next state of q and q not?

@shivangikansal8025 7 жыл бұрын

great explanation and I appreciate that a practical example was also included in the video which made it really easy to understand :)

@ComputerScienceLessons 7 жыл бұрын

Thanks for saying so - I appreciate the feedback

@samsonmayeem8409 4 жыл бұрын

I am offering my college degree i got confused today in my computer architecture lecture.With this video i am now a good "comprehender"! wishe that i get a lot of your tutorials to enhances most troubling concepts. you are a great teacher. Thank you.

@luckypi7327 7 жыл бұрын

BY FAR the best SR Latch and FlipFlop explanation video series on KZfaq! Please keep making videos. Excellent

@ComputerScienceLessons 7 жыл бұрын

That's lovely to hear. Thanks a million.

@Cosmos0000 Жыл бұрын

This is the first video I've come across that explains how these latches actually work and doesn't just input the values of the truth table onto a graphic. Thank you! It finally makes sense.

@russiachan2 4 жыл бұрын

I didn't understand SR latches at all until I saw this. Thank you so much!

@jdb2957 Жыл бұрын

Thank you! Thank you for you hard work, as a scientist and an educator! Thank you for putting the time into these videos! Thank you being British, as sometimes I forget I'm not watching a great BBC documentary! Thank you, Sensei! Thank you!

@ComputerScienceLessons Жыл бұрын

You are very welcome and you are very kind. Thank YOU :)KD

@Bizzon666 4 жыл бұрын

Great video! I have already learned the function of SR latch, but I was confused by different realizations of the circuit which are perfectly explained here.

@shvideo1 5 жыл бұрын

Great Educational video. Comprehensive and clear explanation. Thank you for taking the time and for the quality.

@EmporerAxel 5 жыл бұрын

This is immensely helpful, thank you!

@TopLobster9975 5 жыл бұрын

I'm a distance-learning student going to Arizona State (electrical engineering) and I cannot thank you enough for these videos. It's difficult to get help from the professor as he teaches in the classroom, and the forum we use, Piazza, isn't always an active forum where people get a hold of you quickly. At least I can rely on somebody else's different point of view on this stuff. Thank you very much!

@yodadback 5 жыл бұрын

ASU Industrial Engineering student here i have to take digital design fundamentals. This is a better explanation than my professor.

@mandrewsvideos 2 жыл бұрын

Thanks, this was very useful. I appreciate your explanation of the outputs being denoted as inverse and the explanation of the invalid state. This part gets glossed over in many other people's explanations (probably because they don't have a very deep understanding of the thing they are attempting to explain). Thanks again

@yusufkenanturak1183 2 жыл бұрын

Finally excellent source for Logic Circuit, Thanks from Turkey.

@ComputerScienceLessons 2 жыл бұрын

You are most welcome :)KD

@aghasttoad6916 3 жыл бұрын

My textbook tried to do this in two pages of text with no words. Thank you for making this bearable.

@mohamedhassanin6054 5 жыл бұрын

you're amazing, Mr. Kevin.

@mth32871 4 жыл бұрын

This is one of the best explanations of the SR latch that I have ever seen.

@ComputerScienceLessons 4 жыл бұрын

Kind of you to say so. Thanks :)KD

@HarshaVardhan-we1wc 5 жыл бұрын

this is really good, with clear explanations and the animation used well

@FirstLast-vs1gv 7 жыл бұрын

Great video thanks! Best part is that you switch the inputs in realtime.

@ComputerScienceLessons 7 жыл бұрын

Thanks a million

@EduardoSanchez-lu2sv 2 жыл бұрын

Great video! It helped me understand latches just fine . The example at the end was great. It is definitely amazing what simple binary logic can do !

@E4E 2 жыл бұрын

This is a great series of videos on latches & flip-flops!

@wesdaaawg 5 жыл бұрын

Very concise explanation. Great work sir, thank you!!!

@alejandromedina4540 Жыл бұрын

Clear and concise, it shows just how well you know your stuff. Thank you so much

@ComputerScienceLessons Жыл бұрын

You are very kind. Thank you :)KD

@ethan073 6 жыл бұрын

Dude. This is explained so clearly. The graphics really help a lot too! Exactly what I needed... I'm watching the whole series tonight. Thank you for the time you put into this!!

@ComputerScienceLessons 6 жыл бұрын

Thank you - I really appreciate your comment

@ComputerScienceLessons 6 жыл бұрын

Try not to overdose on it. Little and often is best.

@ryanbay5794 5 жыл бұрын

Clear explanation and visualization. Thank you!

@iloveblender8999 5 жыл бұрын

Great! You saved a lot of my time.

@markfinn825 Жыл бұрын

At 3 minutes and 21 seconds into this video how exactly does someone know that the top output is a 1? When what you need to know is that the top input of the set inputs OR gate is a one when bottom input of the reset OR gate needs to be know first to know that.

@andrewwatts1997 3 ай бұрын

In real life, it's startup state is considdered random. Because any of the two states is determined by wich nor gate is stronger than the other to force a 1 on the output. It's why whenever a cpu starts up all registers need to be reset and put in a known state for it to function propperly. In the video he assumes the top one is set because it helps make the explination simpler.

@ryanopitz846 3 ай бұрын

I have a similar question. How do you know that both of the inputs for the top gate are 0 when the second input of the top gate is dependent on the output of the bottom gate, which is in turn dependent on the output of the top gate? It seems paradoxical. Clearly I'm missing some unspoken rule on the ordering or just misunderstanding something?

@ashenisuranga2915 Ай бұрын

The starting state is determined at the moment the power suplied. its random Q can be either 1 or 0. but once its determined the the other become imedeately the opposite of that .

@albertlewis332 7 жыл бұрын

You are an amazing instructor. I've searching all over youtube and the videos that I've watched are not as clear and coherent as this video. My instructor has explained this concept but as it today after a couple of weeks taking his class, I was completely lost by his inefficient way to teach this "complicated" subject, but as it right now, I finally understand flip-flops and latches but I'm afraid that is too late and I may end up withdrawing from the class that I'm currently taking. One last thing, you are blessed with the gift of teaching. Thank you so much and god bless you.

@ComputerScienceLessons 7 жыл бұрын

Thanks for your very kind comments Aaron. I must admit, I had to do a lot of digging around to get this subject clear in my own mind. The text books I read had a lot of errors in them but I got some fantastic support on the electrical engineering Stack Exchange website. electronics.stackexchange.com/. Ben Eater is brilliant too kzfaq.info. It would be a shame to give up a subject that you might have loved because of one instructor - I hope you make the right decision and that things work out well for you - and good luck.

@joh5853 Жыл бұрын

The animation of the highs and lows are what really helped me understand the concept, great work 🙏🙏

@ComputerScienceLessons Жыл бұрын

Thank you :)KD

@HealthFactoryOfficial Жыл бұрын

you are a life saver, now I understand the concept. Other youtube channesls were going through a lot of what you said like we already knew. This is easy to understand for any beginnger

@ComputerScienceLessons Жыл бұрын

Delighted to help :)KD

@CookCraftandBeyond 4 жыл бұрын

Really commendable job!!! Keep Rocking!!! Saw this video, and immediately subscribed!! I like the way you approached the topic. Great for beginners. Thanks a ton for this!!!

@ComputerScienceLessons 4 жыл бұрын

Thanks for the great comment. Still rocking. :) KD

@Wrtvrxgvcf55 6 жыл бұрын

mate, i dont know how but you made this so incredibly simple for me to understand. kudos

@7hotfuzz7 2 жыл бұрын

My department head teaches Digital Logic Fundamentals and bless her heart she has tons of experience in the industry and has 2 PHDs. She's super nice and extremely helpful but she can't explain a concept concisely to save her life. This is an easy concept that was just presented very poorly to me. Thanks!

@myworldx2684 6 жыл бұрын

Just amazing both the animation and the explaining

@Thinkerko 7 жыл бұрын

wow! your explanation is awesome. thank you so much!

@ComputerScienceLessons 7 жыл бұрын

Tnx

@jonka1 6 жыл бұрын

Brilliantly done thank you.

@christiancompiles5549 Жыл бұрын

Thank you for the practical application at the end!

@hkcamanda6150 2 жыл бұрын

you sir are a life saver...pls continue this awesome work.you are so helpful...probably more than you think

@ComputerScienceLessons 2 жыл бұрын

Thank you. You're very kind :)KD

@roelin360 6 жыл бұрын

I've finally understood! Thanks!

@ninjaweave8779 5 жыл бұрын

Explained in a nice easy to understand way really well, thanks very much! Wish I just watched this video first instead of wasting hours of reading my textbook

@ComputerScienceLessons 5 жыл бұрын

It's great to know it was useful. Thanks for commenting.

@omegapm4699 6 жыл бұрын

These videos are the absolute best

@ComputerScienceLessons 6 жыл бұрын

Tnx :)

@adamhaz2617 6 жыл бұрын

Thank you for the explanation.

@chetnabansal370 3 жыл бұрын

My subject teacher explained it five times, but this one time explanation is worth more than that of five times. :)

@anterkod 7 жыл бұрын

Thank you, good explanation :)

@LovelyStones 2 жыл бұрын

Thank you so much, your video helps a lot. My textbook didn't explain the nor gate and the nand gate well like you did and I came across to your video that I am start learning the flip lops and latches. This video is very great!

@ComputerScienceLessons 2 жыл бұрын

I'm very happy to help :)KD

@Steven-jf4cs 2 жыл бұрын

Wow - a bunch of years later and these videos are still fun 🙂

@ComputerScienceLessons 2 жыл бұрын

Yes - still relevant. Thank you :)KD

@folkertmuntz8719 3 жыл бұрын

These video's are very good. You are helping me through Uni! Thanks!

@ComputerScienceLessons 3 жыл бұрын

I'm delighted to be of service. Thanks for commenting :)KD

@recluse639 5 жыл бұрын

Thank you sir, great work

@dhrubajyotipaul8204 3 жыл бұрын

You explain better than university professors. Thank you!

@ComputerScienceLessons 3 жыл бұрын

You are most welcome. Thanks for commenting :)KD

@Mrkngkw 7 ай бұрын

I needed this playlist. Thank you so much!!!!! LIFE SAVER!!!

@user-vw5nh3dv5j 2 жыл бұрын

Thank you for explaining it so simply!

@ComputerScienceLessons 2 жыл бұрын

You're welcome :)KD

@mattiass4893 2 жыл бұрын

I felt very sophisticated watching this tutorial

@ComputerScienceLessons 2 жыл бұрын

:)KD

@bensmith9253 6 жыл бұрын

Just what I was looking for!

@konradmann5753 3 жыл бұрын

Thank you very much. As said below this video gives a clear and concise explanation. I do appreciated the illustrations, they are excellent.

@ComputerScienceLessons 3 жыл бұрын

Thanks for the kind comment :)KD

@abysmal111 5 жыл бұрын

This video helped me so much. Thank you! =D

@unway1841 3 жыл бұрын

This video is clear and concise. Well done, sir.

@ComputerScienceLessons 3 жыл бұрын

Thank you :)KD

@EngineeringEducation 6 жыл бұрын

Excellent video!

@deepjyotisinha1879 3 жыл бұрын

i was thinking of getting my degree abroad .Thank god i didnt .Thanks dad for not letting me

@khaledmohamed-qm4lk 7 жыл бұрын

very easy Explanation good job

@musicpersempre 6 жыл бұрын

Very useful. Good job!!

@lio_9878 2 жыл бұрын

best video on electronics ive come across so far

@ComputerScienceLessons 2 жыл бұрын

Thank you :)KD

@demdimi9316 5 жыл бұрын

Great videos, hope you keep making more playlists.

@ComputerScienceLessons 5 жыл бұрын

Moe on the way soon

@StevenKarma 6 жыл бұрын

Wow, well done.

@hanif2285 4 жыл бұрын

You've got a subscriber mate, You are wayyyy better than my teacher, and your explanation directly goes to the permanent area of brain. Great Job, well done, God Bless You!!!!! Keep up the good work!

@ComputerScienceLessons 4 жыл бұрын

Thanks for the lovely comment. Please spread the word about my channel. :)KD

@daemiax 5 жыл бұрын

Well, I have always considered the latches as some sort of electronic toggle switches. If the leaver is up the input is one, when the leaver is down, the input is the opposite. So it's like the electronic equivalent of a mechanical toggle switch

@Behdad47 5 жыл бұрын

You saved me 6 months of my life. Thank you

@xeyutipe 3 жыл бұрын

How bro?

@Behdad47 3 жыл бұрын

@@xeyutipe our professor couldn't teach for shit. This video helped a lot.

@xeyutipe 3 жыл бұрын

@@Behdad47 did you finish college yet?

@Behdad47 3 жыл бұрын

@@xeyutipe Nearly done. I hit rock bottom in my life exactly two years ago and still have a few courses to finish.

@emiliogiron7385 2 жыл бұрын

great explanation! thank you so much

@yashkaliapiano 5 жыл бұрын

This is an awesome video. I will happily subscribe.

@rodrigotosaki481 5 жыл бұрын

Beautiful

@brandonsamuelcruzsilva7626 Жыл бұрын

Amazing explanation!

@rubiye 8 ай бұрын

great video great explanation of the application of the latch with the button example

@deelaynee 6 жыл бұрын

This is my favorite video, it puts me to sleep at night!

@ComputerScienceLessons 6 жыл бұрын

I've been putting students in my classroom to sleep for years. Perhaps I'll start a channel of bedtime stories.

@hrishikeshkashyap3715 3 жыл бұрын

Those who are confused, Q= House of 1 & Q°= House of 0. Therefore, if Q has a value of "1", the Latch stores 1. It's because Q is the House of 1. And, if Q° has a value of "1", the Latch stores 0. It's because Q° is the House of 0.

@theidiotwithinternet 3 жыл бұрын

This video is absolutely great

@ComputerScienceLessons 3 жыл бұрын

Thank you so much :)KD

@knowhowstube4751 5 жыл бұрын

you change my life sir

@musatyazvandasara8777 6 жыл бұрын

this is perfect. now making sense

@HamedAdefuwa 4 жыл бұрын

Had this in an hour lecture the other day and understood nothing. So glad i found your channel.

@ComputerScienceLessons 4 жыл бұрын

Glad to be of assistance. :)KD

@abdulmagedkhaled9480 7 жыл бұрын

very useful lesson, keep it up sir :)

@ComputerScienceLessons 7 жыл бұрын

Will do - cheers

@BIRDYCODYT Жыл бұрын

Really thankful for this!

@ComputerScienceLessons Жыл бұрын

You're welcome :)KD

@user-fe1nr3ws1z 5 жыл бұрын

The hardest part how cross linking works is unexplained.

@maxximvigneau444 5 жыл бұрын

This explanation is perfect! Better than my Digital circuits course that I pay $700 for

@sharshabillian 5 жыл бұрын

Found the reason that such pointless sites continue to exist LOL

@a.j.piskor813 2 жыл бұрын

This helped me out greatly on a project, thank you very much!

@ComputerScienceLessons 2 жыл бұрын

You're very welcome :)KD

@JustinCompSpec 6 жыл бұрын

Amazing video.

@josedominguez2021 6 жыл бұрын

Thanks 4 d vdo. Like fabricant!!!! Amazing. One day... i will be like You!!!!!

@davidmilman2850 Жыл бұрын

your videos are really good, and after discovering your channel, it's nearly impossible to go back and learn from other sources. When I discover a video on a particular subject that I need to learn for my degree, I immediately feel relieved and relaxed. So, I just wanted to say thank you for that and keep up the good work! However, if I may, I'd like to make a suggestion. Sometimes it's a bit difficult for me to navigate through your videos and know what precedes what. While everything is relatively organized in playlists, sometimes we learn topics that are integrated into other courses and then there is no match between "reality" and the order in which you present your playlist. This causes me to enter a video and then discover that I need prior knowledge in order to understand it, and then it's a bit difficult to find the preceding video. Therefore, if you could indicate in the description of each video the one that preceded it. Something along the lines of "If you haven't watched XXX yet, here is a link to watch". And so on.. In any case, thanks again and keep doing what you might do best in the world! All the best and happy life.

@markfinn825 2 жыл бұрын

Although I don't like typical latch circuits your videos still seem accurate

@lrl2054 3 жыл бұрын

Well explanation. Thank you.

@davebutler3905 2 жыл бұрын

Very well done lesson. One of the sources of confusion is that the two gates are drawn in parallel. This is elegant but makes it harder to work out the series of events. Just redraw the circuits as two gates in series and it becomes easier to see the positive feedback path and then to visualise the timelines.

@ComputerScienceLessons 2 жыл бұрын

Sounds like a good idea. Next time I teach this to a class, I will ask them to redraw the circuit in the way you suggested :)KD