Experimenting with Buses and Three-State Logic

Let's figure out how to move data around inside our simulated computer. Featuring multiplexers, buses, and three-state logic.
Series playlist: • Exploring How Computer...
Simulation tool (work in progress): sebastian.itch.io/digital-log...
Source code: github.com/SebLague/Digital-L...
Support the channel: / sebastianlague
Resources and Inspiration:
• Bus architecture and h...
en.wikipedia.org/wiki/Three-s...
en.wikipedia.org/wiki/Bus_(co...)
The Art of Electronics (3rd edition)
Music Credits:
github.com/SebLague/Misc-Proj...
Chapters
0:00 Intro
1:33 Multiplexers
3:47 Making a Mess
4:45 Public Transport to the Rescue
6:09 Push-Pull Outputs
9:17 Bus Contention
10:00 Three-State Outputs
12:23 Bus Buffer
14:56 Testing the Bus
18:08 Outro

[@repeater64]

I hope you realise how rare it is on KZbin to have a series that is so genuinely loved by everyone who watches it. Can’t wait for the next one!

[@code_stream_yt]

I inspired for make my own cpu watching this videos! But, i have only 1 question: what is this program? it looks pretty useful!

[@repeater64]

@@code_stream_yt he made the program himself and there are probably links in the description. It’s called Digital Logic Sim

[@idealthinker101]

@@code_stream_yt I am using the android app - "Logic Circuit Simulator" for simulating all this on my phone.

[@feha92]

The dislike button is disabled by youtube, not actually at 0 dislikes.

[@repeater64]

@@feha92 I know… I was more talking about all the positive comments.

[@JDoawp]

A series about electronics would be real cool, you could expand your current program to take voltages into account and add resistors and such to make it more similar to a breadboard.

[@SebastianLague]

I'd definitely love to try making a simple electronics simulation! I'd probably keep it separate from the digital logic sim though, since I also like the simplicity of that.

[@Andy.o52]

@@SebastianLague I also really like the contrast to a real breadboard!

[@dr_mafarioyt4313]

Wait a minute… 17 hrs ago….. wierd

[@ghost4144]

@@SebastianLague Also would be nice to add transistor logic. I am currently using a program called Logisim Evolution to make a 16 bit computer at the transistor level. I have considered writing my own program that would better handle transistor logic but I have no idea how to do that.

[@JDoawp]

@@dr_mafarioyt4313 it's called being a patron baybeeeee

[@lucapalermo7909]

One thing i've always wondered was how the simulation tool itself worked, maybe that could be an interesting video, I'm especially interested about how you save modules that you make and how they are represented in their save files.

[@SebastianLague]

I’ll definitely consider doing a video about it in the future!

[@Yazan_Majdalawi]

@@SebastianLague Yes, that would be great!

[@Alithium0]

@@Yazan_Majdalawi agreed

[@TheGameChangerLord]

@@Alithium0 agreed x2

[@albertoedgar831]

@@TheGameChangerLord agreed x3

[@LarsTheOctopus]

The editing on this video is absolutely stellar. From the smooth grayscale masks, to the animations, to the transitions, I love all the care and love that you put in all those details, it makes it so much more enjoyable to watch 💖

[@SebastianLague]

Thank you! I sometimes wonder if I’m being silly spending time on these sorts of minor details, so I’m happy it’s appreciated :)

[@LarsTheOctopus]

@@SebastianLague Definitely keep it up, but only as much as your motivation allows it 👍

[@CupcakePump]

@@SebastianLague Those "minor" details really take the videos to another level! It's amazing

[@5hirtandtieler]

@@SebastianLague computer topics are typically so bland and obviously technical. Having these sorts of satisfying animations really help with making it enjoyable to watch!

[@Nerdthagoras]

@@SebastianLague No, they make them so much easier to digest.. its why I retain things from your video above others.

[@sutsuj6437]

This series combined with Ben Eater videos is probably one of the best ways to learn about how computers are built.

[@pufthemajicdragon]

Ben Eater fans unite!

[@srivatsajoshi4028]

I am currently doing my degree in electronics and computer systems and that is wholly thanks to Ben Eater. He makes stuff so interesting to learn

[@bartekguch3051]

Im currently building his 8 bit breadboard computer and this series helped me A LOT. So i agree more than 100%

[@Renslay]

Don't forget the wonderful "Nand to Tetris" course!

[@nonchalant_morocco]

AMEN

[@cybroxde]

I keep watching all of these despite having studied this for 4 years. The visual representation is just so satisfying.

[@TechCircuitBreakdown]

Yes, and i like the fact that many of theese things you can build in minecraft, like an alu, a 7 segment display or even a 4 bit register

[@koftabalady]

​@@TechCircuitBreakdownIt makes sense since you only need simple AND and NOT gates to make all of that, which can be done in Minecraft thanks to redstone...

[@odwn]

Hi Sebastian, you probably won't see this but I LOVE your videos. They inspire me to code, thank you for being my inspiration, and favourite youtuber. :)

[@vigneshs.666]

You've ignited passion in me and I breezed through half my sem with this series. Thank you @sebastianlague

[@edht2]

You always motivate me to do more programming! :)

[@terristen]

Lol, I introduce Sebastian to others by referring to him as my spirit animal.

[@vigneshs.666]

@@terristen lolll

[@terristen]

@TooMuchYak yes?

[@catgirlQueer]

the reason the chip has 2 store enables is because that way you could use a row select and column select (for example) without needing a seperate or gate to combine them yourself, it's just a convenience thing

[@Soken50]

That and the fact that chip form factors typically have 2,4,8,16,ect. pins so they would have sat unused otherwise, which is pretty wasteful.

[@Kulpo]

Oh that's really clever. Thanks!

[@aonodensetsu]

it most likely uses a demultiplexer for switching, turning 2 bits of input into 4 exclusive signals

[@dexterwolford]

@@aonodensetsu ur talking about a decoder?

[@aonodensetsu]

@@dexterwolford no, i'm talking about a demultiplexer

[@stan110]

Even though I learned all this stuff at school, I like how you explain this. Simply with lots of examples and then make it more complex.

[@sunbleachedangel]

and it took less than half the length of a lesson

[@dexterwolford]

this and a 15 min mattbatwings video combined can teach more about computers than getting a computer degree

[@rvanagazad3016]

You are a gift from God to us. Being an electronic engineering student, I have learned more information from your videos than my 3 years university classes. Thank you for this amazing series and I hope it will continue that way. God bless you. 🙏♥️

[@stijnveenman]

When talking about the 4 bit register, i think there are 2 reasons for the store signal and data out signal having 2 pins. Firstly, the 16pin dip package is a lot more common then 14, so we likely have those pins anyway. Secondly, when you talk about the issue that 2 chips could output onto the bus at the same time (14:11) this can easily be solved with those 2 pins. If you give each chip a different combination of not gates before their data out, it acts as a mux. A could have no not games, B could have a not on pin 1, c on pin 2, and d on both. Giving you the same inputs as when you had the mux chip. Then they can no longer output at the same time since each chip has an unique combination of inputs to enable it

[@SebastianLague]

Interesting, thank you!

[@reinei1]

Yeah, usually (at least the few chips I have worked with) you get multiple chip selects/out enables to save you a few external and gates. Sometimes you even get one inverted (active low) and one non-inverted because this makes external selection circuitry easier. Also for registers having multiple inputs can sometimes allow easier "stacking" (not really the formal term I think but basically using more than one chip in parallel to increase the bit width or similar), because in these cases some select signals might differ (only have a 8 bit bus but want to work with 16 bit data in this calculation? Easy! Have one "global/external" store connected to one write enable pin on both chips and the other one connected to a toggle latch. This way the first clock pulse will latch the first 8 bit in the first register and flip the toggle latch so the second clock pulse will store the second 8 bit set in the second register.)

[@batimius]

This series is honestly amazing. When learning stuff like this in school, they are nothing but boring information, but when presented this way, everything changes. I don't know why, but seeing all these components work with each is very satisfying. Regardless, amazing series and I cannot wait to see more.

[@arcclite1144]

I like how this series is basically a presentation on my 300 level circuits courses in college. Real blast from the past, and highly educational. PSA if this grabs you, consider a Computer Engineering degree!

[@SaadTheGlad]

Hey Sebastian! I know you probably won’t reply but I just wanna say that you’re literally my biggest inspiration in life. I just made a solar system simulator because I loved yours so much. Thanks for everything :D

[@pufthemajicdragon]

Boosting this comment so it gets seen :)

[@alerlokko2621]

Wish you luck

[@GonziHere]

Thanks for "showing the world" how simple the computer really is. For others: the input signal he generates in the final stage is an assembler instruction (move data from here to there, prepare data to be counted, store the result over there and so on...). Your normal programming language instruction C = A + B gets translated to "move A and B memory locations to input, make their sum, move the output to C memory location" and the only meaningful difference between Sebastian's simulation and your computer is the scale and scale related optimizations.

[@lvlupproductions2480]

That disconnected state blew my mind. I literally paused the video and just fathomed it for multiple minutes, likening it to different revelations like that in different fields such as there being a fourth state of matter plasma, or how there's multiple types of infinities some bigger than other infinities, or back to science molecules not being the fundamental smallest thing and then atoms not being the smallest thing because of quarks and quantum mechanics. I think it's obvious I really like revelations like these thank you so much for sharing one with me. I mean seriously more than two states that a computer uses on a fundamental level?? I'd also like to thank you for the manual transcription, how else would I know it's nybble not nibble, and of course more importantly how would hearing impaired or deaf or blind (through the use of text to speech on actually correct subtitles) be able to enjoy this masterpiece.

[@ChaosContrl]

This series combined with the game Turing Complete makes it perfect to understand and put into practice how a computer (or microcontroller at the moment) works.

[@Obeeron]

For anyone intrested in this kind of electronics there is free project course called '"Nand To Tetris" on Coursera. In this course you build a whole computer starting only with a NAND gate. It's suprisingly easy to follow!!

[@zanbaldwin]

I bookmarked this playlist so long ago, and just realised you've added new videos to it. Your content is amazing and I'll be grateful for anything more that you decide you have the time and energy to release! Thank you!

[@HayKied]

I was totally bummed when I I watched this series before, and it wasn't continued. Thanks for bringing it back!

[@squitz7056]

you are a bright light in the programming community. keep doing you!

[@yun-z]

this is making logic components so intuitive and easy to grasp and remember!

[@Caketacowo]

Absolutely love this series. Can't wait to watch this one. Keep up the amazing videos!

[@Aurarora]

It is always delightful to watch your videos. You can really see how much work and planning goes into them. Great stuff!

[@seanfitz1234]

Love this series

[@landru27]

agreed! I thoroughly enjoyed the first installment, and enjoy even more how each one builds upon the last!

[@gdlifesteal5824]

same

[@purplemosasaurus5987]

Video: 1 hour ago Your Comment: 23 hours ago

[@seanfitz1234]

@@purplemosasaurus5987 Patreon early access

[@purplemosasaurus5987]

@@seanfitz1234 I expected that to be the case...

[@konstantinsotov6251]

Wow, I am so glad this series continues on! It is really interesting, can't wait for the next part!

[@DaRealNim]

This series is just awesome, I can't wait to see how far you'll go. Also, I can just hear your smile in your voice and it's really awesome, I wish all people were this enthusiastic about the things they teach

[@shidobu]

Another great video! I could seriously listen to you explain anything and be fascinated the whole time.

[@jordanray1537]

Absolutely loved this episode. When you put that calculator together and showed it storing numbers, doing basic calculations and displaying the results, I finally saw the computers we have today emerging. Awesome stuff!

[@vibaj16]

I know pretty much all this, but I still love watching this series due to how well-made it is, and to see you learning it!

[@Mrqwerty2109]

I absolutely love this content. Each upload I am looking forward to, as I want to see the progression of technology further and further, all starting from simple logic. Thank you for making this!!!

[@Khoriume]

Just found this series and it is great! I enjoy how it focuses on the theoretical part (not having to worry about timings or electronics too much) but also mentions the more practical problems as well. Great work

[@nocturn9x]

Again, literally a computer architecture course but so much friendlier. I love it!

[@notnullnotvoid]

I've never seen it all put together like this before. When you wired everything up at the end and started (essentially) running CPU instructions by hand, I got goosebumps. Just beautiful.

[@tristanshort3547]

This series is absolutely amazing! Keep up the good work!

[@LHS_Shadow]

I hope that part 5 will be coming out soon, love this series so much! :)

[@boris3320]

I love your "simple" logic sim ! It's amazing to see & experience how a complex function emerges from a basic set of gates.

[@adixx328]

I love this series, can't wait for the next episode!

[@IanWagner94]

Please, continue with this series. It's so well explained. Just found your channel and it's just so well done. Congratulations and thank you very much for this explanation!

[@vojtaondracek8571]

Love this series! I really appreciate how illustrative it is about the problems. Can't wait for another video. Keep up! ❤️

[@hubertk7363]

I'm enjoying how your little simulator made for this series is improving every video.

[@embergamedev]

I've always been interested in building my own 8 bit computer in video games with logic gates and eventually building one in real life. I've watched Ben Eater's channel which is absolutely marvelous in explaining complex details. Your channel has been a good buffer for me as sometimes watching other videos on the topic gets complicated quickly. You explain everything so well and the visualizations really help so so much with my understanding of the topic. Thank you for these awesome videos!

[@sirvandorlot169]

This series is amazing. You made an amazing visualization tool and these videos explain so many ideas on the basics of computers so clearly and concisely. I'm excited for the next video in the series.

[@MirageDev_]

This series is brilliant! I love watching it whenever a new video comes out. You're a great teacher. Thanks for all of your videos.

[@editxswajal]

Please continue this series plz 🙏

[@bismuthnickel]

Finally! An update to the series that taught me college level stuff in the 4th grade.. I love this series and would love more of these videos. Thank you Sebastian, for fueling my nerdiness.

[@thebellian]

Just happened across this series today and i'm loving it!! Your voice is so soothing along with the music in the background. And your explanations are done in a way so that someone as illiterate as i am on this side of things can follow along. Can't wait for the next one!!

[@Dremth]

The visuals on these videos are so good. Concise, yet unambiguous. I already know all of the stuff this series covers, but the videos are just so well made, relaxing, and satisfying. It makes me really wish I had these videos when I learned this stuff to begin with.

[@kireitonsi]

I dropped everything to watch this the moment I got the notification!

[@MsDimalo]

Sebastian slowly becoming Ben Eater

[@Mythricia1988]

He's being consumed... Eaten, you could say.

[@bradleyfallon6847]

You're a hero! This was such a good series. The way you demonstrated everything on your simulator, which was designed to be very easy to read, made this really easy to follow. Also, it's cool that you actually made a simulator and didn't just draw diagrams.

[@808scum]

This has been such a cool series. The progression to this point has been so smooth, you can tell you put a ton of thought into it! Can't wait to see more

[@infinite_cows]

this is some of the highest-quality educational content on the platform

[@reallySmooll]

The mouse movements are so smooth, I thought this simulation was made in editing software.

[@samuelhulme8347]

Maybe his mouse was? - and just perfectly timed the clicking to when he clicked with the real mouse

[@shmunkyman33]

The mouse movement was definitely automated in some way, not sure if it's actually a part of the circuit simulator code or some other program that automates the mouse, but it's too smooth to be real inputs

[@JackAllpikeMusic]

Love these videos so much Sebastian. You have such an incredible way of teaching, in such a clear yet intriguing way. I'd love to see more of these. :)

[@GearsDatapacks]

I really hope you continue this series. I'm super excited to continue learning about all the complex things you can create from just some simple chips wired together in clever ways

[@fabiovokrri517]

This man turned electronics into art

[@matthias916]

Exploring microcode to simplify/automate the testing you did at the end would be a cool way to build up to a CPU

[@jetison333]

Im almost positive thats exactly the route this series is going to take and im super excited for it!

[@matthias916]

@@jetison333 would indeed be really cool to see. Sebastian is starting to look more and more like Ben Eater and I'm all for it

[@srivatsajoshi4028]

@@matthias916 Ben Eater and Sabastian Lague are the best youtubers I've seen

[@PaulSpades]

The instruction format in this case is really funky: 4bit - external memory/stack/input in red, 4bit - read address in blue, 3bit - operation type or store address in indigo. But you can make an instruction decoder and design something more elegant if you want to, just grab the software and make your own. What the circuit in the video really needs is more explicit branching with a comparator. But you'd probably add a small stack and stack pointer with that, to make sure it's Turing complete. At this point the circuit simulator devolves into a CPU architecture designer with no way to synthesize the design.

[@ac3_train3r_blak34]

These explanations are so good. I nearly cry from relief every time I see how much easier you've made learning this stuff.

[@LukeOr98]

I've been a software engineer for like 7 years at this point, and I've always abstracted in my mind the behaviour of this low level components... this is the first time that I get to understand how all of this works from the bottom up, and it's SO cool. Be sure that i'll send a lot of people your way, because this is pure gold.

[@asynts]

7:02 The two store inputs are effectively a free "AND" gate. If you don't need it you just wire them together.

[@timwhite1783]

I'm curious how far you'll go with this stuff. Can very easily see you designing and building a 16 bit CPU and writing some instructions for it.

[@Kaldorey]

Been following your series since the beginning and I love the way you teach the subject ! I'd definitely be interested in videos on electronics aswell, as I believe it makes the link with the "real world" clearer. Kudos for the great work Sebastian !

[@Adipose69]

I love this series so much! A deeper dive into electronics would be really useful to a lot of people, I'm sure, myself included. Thank you for making these videos.

[@182exe]

I cannot stop wondering how you move your mouse cursor so perfectly. Every line is perfect, and every movement is smoother than a sin wave.

[@laesseV]

couldn't you use a 2 bit number to encode the 4 output selection bits so that illegal states (two outputs selected the at the same time) and bus congestion become impossible?

[@samuelhulme8347]

That would be possible to .

[@rmichaeldeutsch]

Yes, that would solve the issue of bus contention, but would limit your design to only working for 4 registers. This approach (while somewhat more "risky") allows for much greater modularity.

[@hossamel2006]

Please continue this series I really missed it ❤

[@veylenn]

Your educational style is fantastic. Thank you for making these videos.

[@milansatters8750]

These video's are really great, You explain everything so clearly and the mix of visual and audio explanation really makes it very understandable to everyone, great work. Keep it up!!

[@samarthtandale9121]

Really love the series ❤❤❤❤❤ Please make more! *Thank You* 🙏🏽

[@GustavoZIMBA]

your videos are so therapeutic, I fell like I'm relaxing the same time I'm learning a lot of things. Great video!!

[@iamasquidinspace]

You sir are single-handedly teaching me a subject I never grasped before and had lost all hope to ever understand. Thank you very much!

[@jamescunningham4528]

I love this, its so awesome. I get so happy when I see a new video of this series uploaded. Keep it up!!!

[@larmkaartdev7944]

Im a big fan of this series! Because its simplicity it's very easy to follow, can't wait for more!

[@tristandreemurr8755]

You sound like you're in a calm, understanding, teaching smile throughout the narration. It brings a calm, along with the music, that makes me feel like learning.

[@pastafarian7]

I love your circuit diagrams and narration. Great video

[@TheBlownapart]

I have very little understanding of what's going on, but the editing quality, visuals, and your calm voice make these videos so enjoyable to watch. Thank you so much for this series and all the work you put into it.

[@Pistaschios]

Man this serie is a banger really. And small reall life build to explain thing in the real world is such a great thing ! Those videos must takes you a lot of time and efforts but I hope you'll keep going. I cannot think of a better learning material than this. Thank you so much !

[@celsient]

my jaw dropped in the final few minutes, seeing the culmination of everything so far working flawlessly. this series is so brilliant, thank you for all of your effort!! (and thank you for the subtitles. i have some speech-comprehension difficulties and really appreciate well-crafted subtitles :] )

[@user-he1rn5uu5w]

This is so awesome! I wish we had these at school so we can practice at home, without the need to worry about wires and chips flying around. And the ability to bundle up logics into your custom chip is just amazing.

[@WenhopOfficial]

God I love this series! It’s really nice to see how you’re explaining pretty advanced computer science in a simple-ish way.

[@Miszkaaaaa]

Wonderful video, takes me back to my first years on uni, but gives incridible level of joy with the quality and fun of creating own components like this!

[@jimbowondall]

I can't get enough of your channel, I've been watching for years and you've inspired me to study a diploma in programming (which I'm currently half way through and absolutely loving), thank you :)

[@rhythmatician4411]

I've always wondered how logic gates and chips worked when it came to current and positive/ground. This is the best explanation I've seen! Having another series about electricity would be very welcomed. I love your approach to teaching this kind of stuff!

[@bastian3461]

ive been really loving this series of yours amazing

[@ThumbsTup]

I literally just saw your last video on this topic yesterday, I'm glad I can immediately continue today

[@minefacex]

Amazing quality video, thank you! I think this is the first time I have really understood what is the floating state!

[@rexroyulada6267]

Each video always hooks me in, thank you for making learning logic gates so entertaining!

[@ntnzelenin]

These series are amazing and I want to say a big thank you! You explained the basics in a very simple and entertaining way, which sparked my interest in microelectronics and now I have a new hobby. I decided to take the course " From Nand to Tetris" that you also mentioned in order to learn the subject in more depth and hopefully will have a couple of pet projects related to the field

[@sobitkarki6030]

Its so awesome that you're still continuing this... dont stop ever if possible...

[@MrAdBounty]

I can't get over that everything that you add and link is always perfectly align My OCD is grateful !

[@onusmusicboers2885]

Looking forward to the next video in this series!

[@heatblayze]

Thank you as always, Sebastian!

[@Dominik-K]

I would love to see a series about electronics by you. Your style of explaining IT topics is very enjoayayand easy to understand. Great job with this video too

[@andrewhayden987]

An extended series would be great! Love your work!

[@TrideGD]

This is such an incredible series, explains everything just so perfectly, absolutely 0 confusion from me!

[@coolnj4]

Loving this series so far

[@DominikFeiler]

Absolutely amazing. Great video!

[@msclrhd]

Thank you for the excellent explanation of tri-state buffers -- both how they work and why they are important.

[@yogenrai5651]

yes sir its fascinating looking forward to learning more from you