When I got introduced to the d-latch, the non-data input was called 'enable' instead of clock, which makes a lot more sense to me because the d-latch is not edge-triggered like a flip-flop, but can change its value whenever enable/clock is set to 1 and not just at the exact moment when it goes from 0 to 1 (posedge). So. Voting for 'enable'!
I couldn't agree more! I was very confused between latches and flip-flops in the initial days of my semester. Some people(including some professors at my uni + on the internet) took little to no care while talking about latches and flip-flops and would often use the terms interchangeably. Enable for latches ftw!
Benevolent critique: So at about 3:45 he starts drawing. The angle of the camera puts his hand directly between the lens and his drawing, so all we see is his hand moving around while he talks. A better shot might to be to film this from the other side of his desk, so the hand, drawing, and paper are visible. They'll be upside down in this shot, so you would rotate it 180 degrees for final cut. That way we can see him draw and point with the pen/texter while he speaks, and no rigging is required to get the camera directly above. Just a thought, I've not tried it.
Also, in the shot where the viewer was supposed to see the wires on the mainboard, I didn't see much and the editing was more akin to music videos than documentaries.
We need more of these videos explaining electronics and computer engineering, how these devices work under the hood, and where do the bits go. It would be very nice if we would see a series on FPGAs and Hardware description languages, and Digital Design.
Your graphics are good these days, Brady. They lagged a bit behind the quality of your editorial output in the past. Glad you're going from strength to strength as I think your channels are among the jewels of the interwebs.
I really like this channel because I do computer engineering in my country i'm only in the second semester so I don't know much but in your videos I kinda understand more complex things that I'll learn in the future.
Great explanation of latches and clock signals! A humble request: Could Computerphile and Dr. Bagley maybe make a video on ripple-carry adders and Kogge-Stone adders and the difference between the two?
KuraIthys I agree that they are simplified model, however it provides a great degree of similarity to the solely logic part. This gates when made in Minecraft gives the player excellent visualization of what is going on. For example, for an SR latch, instead of looking at two weird shapes with crossing lines, in MC what you do is simply placing two blocks (OR), two torches (NOT), and two dust (wire). This game lets you actually understand what is going on, and I believe it serves a great educational purpose and deserved to be featured on this channel. That's only my opinion though of course.
sarowie yeah i recall people saying *insert 9yo voice* WOAH I THOUGHT RS-NOR LATCH MEANT REDSTONE-NOR LATCH and even worst WOAH THEY HAVE THIS DESIGNED BASED ON MC'S RS-NOR AND HAVE THE SAME NAME Which is why i call them SR nor latches
But don't forget We can add mods (Project:Red mod/redpower[obsolete]/redlogic) that adds in premade logic blocks We can use torches and rs to teach basic logics, and then move on to compacting it and making bigger logics. Also, this components do use the proper terms (sooommewhat) and less of an hassle than Vanilla MC RS
Yadobler Despite the fact that they are referring RS as "redstone", isn't a good thing to hear from a nine year old talking logic gates? This really proves the success of introducing these binary gates to the young generations.
Working with the Nintendo Entertainment System in my spare time, it's very useful to watch this! I get to learn how, and why some of the hardware works the way it does, and how bankswitching logic can be built (as it can only address 32kB of program at a time by default)
Simon Vetter half a minute is not adequate and explaining them together with barrelshifters is a bit of a mess, as shift register and barrel shifters do the same task, but in very different ways. I think a topic like Ring counters (Overbeck counter and Johnson counter) would be a better illustration for shift registers. Especially as their effect with a few leds connected to the output is quite nice to look at.
sarowie I agree with this, ring counters aren't too complicated to go from regular shift registers. Also I disagree with that other comment about shift registers only going for half a minute since there are explanations of applications as well as counters.
I just made my first successful T-flip flop in Minecraft a couple of days ago. It took a lot of effort and a lot of space, but I managed! The purpose of this, you ask? To have a button for turning the lights on or off in my room, of course...
Derek Leung yeah I know, but I don't want to hear the piston go off every time I switch the lights on or off. I didn't really do it fo practical purposes, more for the fun of it, as you might have guessed =P
Could you do a video explaining some of the design considerations/decisions with regard to the Linux kernel/based OS? This is nearly impossible to find on search results. :-(
I beg for a bit more differentiation between different memory types and usages. This kind of circuitry is useful to build shift registers, counters, multiplexers, code convertors etc. But it is only remotely related to the SDRAM that is used in computers today or NAND-Flash devices like thumb drives and SSDs. This video is very miss leading in the sense that it leads people to believe that the RAM in their computers is built using flip flops based on NOR-Gates (That would be SRAM). That's not the case. DRAM is used in contemporary computers which uses only a singel transistor (Compared to SRAM using 4 to 6 transistors) and a capacitor to store information and is periodically refreshed due to the capacitor loosing charge over time. Because DRAM is cheaper and more space efficient, it has replaced the SRAM in many applications. SRAM has some other advantage tough: it is extremely energy efficient and allows faster access times than DRAM. It is therefor primarily used in applications where speed and energy efficiency is more important than space and manufacturing costs. Namely CPU cache, processor registers, FPGAS, small lowpower memory (eg. BIOS chips). Would be nice if you could feature this in a future video =)
That's good to know, because when I was taught about about computer memory in my apprenticeship, we were not told which is used for what. Had to finde out by myselfe. Then in an other course they taught C and Assembler on micro controllers. We learned how to use memory an registers, timers, counter etc. but no one ever talked about the actual hardware. Bit of a shame really. I am currently in my first term studying cumpter science and I am planing to specialise in embedded systems. I hope they will do a better job.
Okay, so... you've described how a D-latch works in the circuitry, but how does a flip-flop work? What gates are wired together, and in what way, to make a low-to-high transition the "store" trigger?
It's simple really, though I'm not sure why they didn't cover it in the video. You take two D-latches, connecting Q from the first latch to D of the second latch. Then you wire the clock to the clock input of the first latch directly and invert the clock signal before connecting it to the clock input of the second latch.
Sokar Oh. So I assume, then, it works on the same "slight delay" principal that makes latches work at all? Where the slight delay in a changing clock signal from one latch to the other is what allows it to "capture" the changed data before the second latch's clock signal goes low?
Not exactly, it would work under the assumption that the clock reaches both latches at the exact same time. The circuit I described before was for a falling edge D-flip flop, so it would save the data when the clock signal goes low. If you put the inverter on the first latch, it becomes a rising edge DFF, so it should be a little easier to conceptualize. In that case, when the clock is low, the first latch would always transparent and change with the data line, but the second latch would be frozen on the last data. If the clock signal goes high, the first latch will freeze on the last value of D it saw and the second flip flop will save that value from the first FF. The only time after that where you can save another value is after the clock signal goes low and high again.
So when some company claims "100 GB memory storage" does that means there are 800 billion flips flops (1 byte = 8 bits and giga refers to billion)? and how would you save a number thats more that 16 bits since there are 16 data lines in a modern computer like u said.?
Difficult to follow when he presents flip-flops as the hand covers the drawing until the end. Wouldn't it be better to shoot from the other side and then flip the image?
HELP. I'm struggling with the camera work. Cutting away before he has finished an illustration, showing the back of his hand instead of the drawing, jumping around like a caffeine junky doesn't help at all. Ok I can pause and rerun , but I am trying to listen as well. Otherwise glad to have found this.
+Andrew Taylor I do the subtitles myself (have the odd helper now and then who do it for a favour) - have only just started going through all the videos - it's taking a long time, please bear with me but I'll try to do this one next >Sean
Computerphile always uses a nerdy looking thumbnail to make it seem like the content is more intelligent or mystical than it is.. It's a pretty cheap psychology trick to fool the masses of sheep :P Think about it, if they put a well groomed and well dressed person as the thumbnail, people would assume that the subject is not very difficult. I've always been into math, engineering, computers, etc., but people always treated me like I was oh-so-smart back before I dressed well and groomed myself. Not so much anymore (not complaining, but it is annoying how we judge people based on looks). I'm guilty of it too I guess.
When I got introduced to the d-latch, the non-data input was called 'enable' instead of clock, which makes a lot more sense to me because the d-latch is not edge-triggered like a flip-flop, but can change its value whenever enable/clock is set to 1 and not just at the exact moment when it goes from 0 to 1 (posedge).
So. Voting for 'enable'!
current uni student in CS, I can testify I learned it as “en”, which stands for enable
I couldn't agree more! I was very confused between latches and flip-flops in the initial days of my semester. Some people(including some professors at my uni + on the internet) took little to no care while talking about latches and flip-flops and would often use the terms interchangeably. Enable for latches ftw!
ok?
Benevolent critique: So at about 3:45 he starts drawing. The angle of the camera puts his hand directly between the lens and his drawing, so all we see is his hand moving around while he talks.
A better shot might to be to film this from the other side of his desk, so the hand, drawing, and paper are visible. They'll be upside down in this shot, so you would rotate it 180 degrees for final cut. That way we can see him draw and point with the pen/texter while he speaks, and no rigging is required to get the camera directly above.
Just a thought, I've not tried it.
Also, in the shot where the viewer was supposed to see the wires on the mainboard, I didn't see much and the editing was more akin to music videos than documentaries.
I love this series on computer circuits! I hope you eventually progress and advance all the way to modern chipsets.
We need more of these videos explaining electronics and computer engineering, how these devices work under the hood, and where do the bits go. It would be very nice if we would see a series on FPGAs and Hardware description languages, and Digital Design.
0:38 error. S and R should be exchanged in the drawing to make valid the statement: "when S goes high, Q goes high"
:) I'm glad to see that there is someone that notice that error
Your graphics are good these days, Brady. They lagged a bit behind the quality of your editorial output in the past. Glad you're going from strength to strength as I think your channels are among the jewels of the interwebs.
Rob Bowman Hi Rob, the kudos goes to Sean Riley who makes these videos... >Brady
I really like this channel because I do computer engineering in my country i'm only in the second semester so I don't know much but in your videos I kinda understand more complex things that I'll learn in the future.
Great explanation of latches and clock signals!
A humble request: Could Computerphile and Dr. Bagley maybe make a video on ripple-carry adders and Kogge-Stone adders and the difference between the two?
Looks like exactly the same as how they store data in those Minecraft computers. Really learned much playing with those redstone stuff.
Yes... Those are modelled on real computers. Redstone seems to be a very simplified model of how electricity works, so it kind of makes sense.
KuraIthys I agree that they are simplified model, however it provides a great degree of similarity to the solely logic part. This gates when made in Minecraft gives the player excellent visualization of what is going on. For example, for an SR latch, instead of looking at two weird shapes with crossing lines, in MC what you do is simply placing two blocks (OR), two torches (NOT), and two dust (wire). This game lets you actually understand what is going on, and I believe it serves a great educational purpose and deserved to be featured on this channel. That's only my opinion though of course.
sarowie yeah i recall people saying
*insert 9yo voice*
WOAH I THOUGHT RS-NOR LATCH MEANT REDSTONE-NOR LATCH
and even worst
WOAH THEY HAVE THIS DESIGNED BASED ON MC'S RS-NOR AND HAVE THE SAME NAME
Which is why i call them SR nor latches
But don't forget
We can add mods (Project:Red mod/redpower[obsolete]/redlogic) that adds in premade logic blocks
We can use torches and rs to teach basic logics, and then move on to compacting it and making bigger logics. Also, this components do use the proper terms (sooommewhat) and less of an hassle than Vanilla MC RS
Yadobler Despite the fact that they are referring RS as "redstone", isn't a good thing to hear from a nine year old talking logic gates? This really proves the success of introducing these binary gates to the young generations.
Working with the Nintendo Entertainment System in my spare time, it's very useful to watch this! I get to learn how, and why some of the hardware works the way it does, and how bankswitching logic can be built (as it can only address 32kB of program at a time by default)
Videos like this really help with my ECE studies, thank you!
It always feels strange to be here so early!
Shift registers would be an interesting topic to follow up after these introductions to flip flops. I enjoyed first learning about those haha
But they're not that complicated, are they? Could be explained in half a minute, I reckon. Perhaps together with barrelshifters?
Simon Vetter
half a minute is not adequate and explaining them together with barrelshifters is a bit of a mess, as shift register and barrel shifters do the same task, but in very different ways.
I think a topic like Ring counters (Overbeck counter and Johnson counter) would be a better illustration for shift registers. Especially as their effect with a few leds connected to the output is quite nice to look at.
sarowie I agree with this, ring counters aren't too complicated to go from regular shift registers. Also I disagree with that other comment about shift registers only going for half a minute since there are explanations of applications as well as counters.
4:59 Am I the only one who laughed as if Steve had just ripped a board out of his PC?
I just made my first successful T-flip flop in Minecraft a couple of days ago. It took a lot of effort and a lot of space, but I managed! The purpose of this, you ask? To have a button for turning the lights on or off in my room, of course...
The make a t flip flop in minecraft, simply send a one tick pulse to a sticky piston, with a power source directing into the block. ;)
Derek Leung yeah I know, but I don't want to hear the piston go off every time I switch the lights on or off. I didn't really do it fo practical purposes, more for the fun of it, as you might have guessed =P
I have to design a 3 bit binary to decimal counter for a uni course, and that video helped a lot. Thanks!
i could watch hours of videos on that subject!
Please add the prev video link in the description, links in annotations are not available on mobile/tablet
done - sorry for the oversight! >Sean
Thanks Sean!
Hehehe literally the first person on youtube to ever actually use the description box, well done! :D
I like this kind of videos where people teach computer enginering on big scale ( 16 DIP ) chips, this even helps to undersand c programming better :)
Cool vid on Ram. Feel free to also do some stuff for DDR4
i really enjoyed watching the video,and if only they will be a video about the RAM (random access memory).
How do you determine the initial states of the bottom input of the top gate or the top input of the bottom gate ?
Could you do a video explaining some of the design considerations/decisions with regard to the Linux kernel/based OS? This is nearly impossible to find on search results. :-(
I had an exam on digital logic a few days ago. One of the question was to implement a 2-bit multiplexer using Nand gates . Pretty easy , but fun :)
I beg for a bit more differentiation between different memory types and usages. This kind of circuitry is useful to build shift registers, counters, multiplexers, code convertors etc. But it is only remotely related to the SDRAM that is used in computers today or NAND-Flash devices like thumb drives and SSDs. This video is very miss leading in the sense that it leads people to believe that the RAM in their computers is built using flip flops based on NOR-Gates (That would be SRAM). That's not the case. DRAM is used in contemporary computers which uses only a singel transistor (Compared to SRAM using 4 to 6 transistors) and a capacitor to store information and is periodically refreshed due to the capacitor loosing charge over time. Because DRAM is cheaper and more space efficient, it has replaced the SRAM in many applications. SRAM has some other advantage tough: it is extremely energy efficient and allows faster access times than DRAM. It is therefor primarily used in applications where speed and energy efficiency is more important than space and manufacturing costs. Namely CPU cache, processor registers, FPGAS, small lowpower memory (eg. BIOS chips). Would be nice if you could feature this in a future video =)
Don't Panic!
We'll get there… :)
That's good to know, because when I was taught about about computer memory in my apprenticeship, we were not told which is used for what. Had to finde out by myselfe. Then in an other course they taught C and Assembler on micro controllers. We learned how to use memory an registers, timers, counter etc. but no one ever talked about the actual hardware. Bit of a shame really. I am currently in my first term studying cumpter science and I am planing to specialise in embedded systems. I hope they will do a better job.
That motherboard is an Atari 520ST.
Okay, so... you've described how a D-latch works in the circuitry, but how does a flip-flop work? What gates are wired together, and in what way, to make a low-to-high transition the "store" trigger?
It's simple really, though I'm not sure why they didn't cover it in the video. You take two D-latches, connecting Q from the first latch to D of the second latch. Then you wire the clock to the clock input of the first latch directly and invert the clock signal before connecting it to the clock input of the second latch.
Sokar
Oh. So I assume, then, it works on the same "slight delay" principal that makes latches work at all? Where the slight delay in a changing clock signal from one latch to the other is what allows it to "capture" the changed data before the second latch's clock signal goes low?
Not exactly, it would work under the assumption that the clock reaches both latches at the exact same time. The circuit I described before was for a falling edge D-flip flop, so it would save the data when the clock signal goes low. If you put the inverter on the first latch, it becomes a rising edge DFF, so it should be a little easier to conceptualize. In that case, when the clock is low, the first latch would always transparent and change with the data line, but the second latch would be frozen on the last data. If the clock signal goes high, the first latch will freeze on the last value of D it saw and the second flip flop will save that value from the first FF. The only time after that where you can save another value is after the clock signal goes low and high again.
Where is this previous video about nor gates he mentions right at the start?
I think it's this one: /watch?v=XETZoRYdtkw
@thecassman Thank you
Thnx man this is really handy!!! ;)
4:15
this one?
There is no link to the previous video.
fixed now - How Computer Memory Works (Part 1): ruclips.net/video/XETZoRYdtkw/видео.html
>Sean
So when some company claims "100 GB memory storage" does that means there are 800 billion flips flops (1 byte = 8 bits and giga refers to billion)? and how would you save a number thats more that 16 bits since there are 16 data lines in a modern computer like u said.?
Sounds like computer engineers really like the D.
haha, JK.
Props if you got all 10 jokes.
S and R or Q and not Q are the wrong way around, S goes to not Q gate and R goes to Q gate.
Difficult to follow when he presents flip-flops as the hand covers the drawing until the end. Wouldn't it be better to shoot from the other side and then flip the image?
Yes, this feedback has been taken on board - although flipping the image would flip all letters and numbers too >Sean
If flipped just once, but not if flipped again in the other axis or simply rotated 180 degrees.
Cool
AWESOME video, but I didn't get the difference between simple D latches and flip flops
Seems like S and R are not at their correct positions. They should be interchanged.
I think so as well.
This makes no sense, the circuit is invariant under mirroring.
In the part I video, the Reset was on top and and Set was on the bottom.
ALU please
HELP. I'm struggling with the camera work. Cutting away before he has finished an illustration, showing the back of his hand instead of the drawing, jumping around like a caffeine junky doesn't help at all. Ok I can pause and rerun , but I am trying to listen as well. Otherwise glad to have found this.
Neat!
you can make these all in minecraft. it's a good time
Looks like you got Q and Qbar the wrong way round.
SUPERRRRRRBBBBB.
WOW.
GREATTT!!!!!!!!
nice shirt though
He reminds me of The Adoring Fan (Google it)
Wireworld.... lets you see all the data in motion, so to speak.
So, you could...somehow make a computer, or at least a memory "chip" that runs on running water and a mill, no wires involved? From wood, of course.
wat
I actually made 4 bits of RAM for my arduino using RS latches. As you can tell, it sucked, and was a tad bit of a waste of money.
Delilah
sanababich
Why isn't this video closed captioned? I'm deaf and I don't appreciate being left out. I need to understand how this works for my class.
+Andrew Taylor I do the subtitles myself (have the odd helper now and then who do it for a favour) - have only just started going through all the videos - it's taking a long time, please bear with me but I'll try to do this one next >Sean
u like cucumber?
ok bye
Computerphile always uses a nerdy looking thumbnail to make it seem like the content is more intelligent or mystical than it is..
It's a pretty cheap psychology trick to fool the masses of sheep :P
Think about it, if they put a well groomed and well dressed person as the thumbnail, people would assume that the subject is not very difficult.
I've always been into math, engineering, computers, etc., but people always treated me like I was oh-so-smart back before I dressed well and groomed myself. Not so much anymore (not complaining, but it is annoying how we judge people based on looks). I'm guilty of it too I guess.