EEVblog #1249 - TUTORIAL: Timing Diagrams Explained

A tutorial on how to read timing diagrams. An essential skill for designing and understanding digital logic, FPGA and microcontroller designs and datasheets.
Logic Analyser Design: kzbin.info/www/bejne/n6i1mamegK-fsNU
Digital logic datasheets explained: kzbin.info/www/bejne/qaOUdYJ-o6-cbqs
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[@Mtaalas]

Once again a topic that I would have killed for when I was a student :) Keep them coming, you're doing an amazing job. EE is still something there's very little real teaching material online that's RELIABLE and coming from a real EE :)

[@shifter65]

Love the distilled knowledge in this video. Years of experience summed up in less than an hour.

[@idkEngineering]

This is the kind of content that got me into your channel when I was back in high school! Great to see it more of it!

[@EEVblog]

Thanks.

[@Radiofreak1041]

9:11 That's called a zero se-tup time, so that means that there's zero set-up time. Thanks Dave! ;)

[@gagnon124]

My prof added a link to this video to help us understand the concept. So now it is school work to watch the EEVblog :).

[@tomservo5007]

perfect timing (no pun intended) , I was looking for tutorials. Thanks Dave!

[@Aemilindore]

So glad to see a educational video from you. Had been missing them for a quite awhile. Thanks Dave. Lots of things to learn.

[@alexandermonro6768]

Another great video. I've been playing with this stuff for more years than I care to remember, but you always seem to show some details that I was never clear about before. More tutorials please, and thanks for all the ones so far!

[@kevincozens6837]

Good tutorial as always, Dave. I've been reading timing diagrams for decades. Timing diagrams for microprocessors are fun to look with how they are marked up. They can look quite intimidating to the newbie. Always interesting deciphering address and data bus set up and hold times.

[@Flyboy737]

Dave, Keep making Videos like this. Much appreciated in the time and effort you put into these type videos. I haven't had the need to work with timing diagrams as much as I used to but they are very good for review for a very worthwhile subject!

[@twjonckheere]

I still remember the first time I discovered timing diagrams when working with SPI communication between an Arduino and a digital potentiometer. I bought a logic analyzer to study the timings and worked through getting it to work. One of my top moments in learning electronics for sure.

[@JakobWierzbowski]

Thanks Dave, you had the right timing :D for this video

[@hadireg]

nicely explained Dave! Thanks for such relaxed and high quality content!

[@rhama8751]

An excellent fundamentals video, thank you.

[@joetke]

A pretty good reminder... Thank you!

[@wolfz9146]

Thanks again this sort of topic is always useful and could be a great series.

[@TimeWasted8675309]

This is a perfect video. So much good information. Thank you!

[@Car_Ram_Rod]

I could have used this last semester!!!! Great video as always dave!

[@drruncmd]

Love the explanation but my head still hurts! Good job as usual Dave!

[@IsaacMorton]

Very helpful! I've kinda just been guessing my way through those up till now. Very informative!!

[@EEVblog]

That's what almost everyone has to do!

[@testep02]

I'm sure this is info that you take for granted, Dave. But for hobbyists like me, trying to learn to read these things on my own was a BEAST! It took me forever to get good at reading them. These videos are PURE GOLD!!

[@EEVblog]

Yeah, it's not something you learn in school either, it's just assumed that you'll get it eventually.

[@jon87386]

I was just developing some timing diagrams, too! This is perfect

[@NielsHeusinkveld]

Perfect timing you would say?

[@mirmbloatbust4783]

Excellent! I just spent the yesterday evening trying to recover an Atmega644 by programming the fuses manually. Had no luck, but now I have few ideas where I may have screwed up.

[@wpherigo1]

Like you, I did a lot of that in the late 80’s and early 90’s. And as you said, it wasn’t just for set up and, but also to help you understand the logic of what was happening. Indispensable for both design and troubleshooting,

[@dentakuweb]

I like it when diagrams have dotted vertical lines in them. It makes it much easier to see which clock or at least which edge of the clock data further the page lines up with.

[@db-jw6ig]

Excellent! For part two may I suggest an example using 'scope/logic analyzer with hardware.

[@Varde1234]

Enjoyed the video Dave!

[@danielfromca]

Thank you this is very helpful

[@rodneyshinkfield9465]

Thanks, Dave! From here in England, most (sorry, all! lol) of the video went above my head - well I am 74! But I couldn't stop watching until the end.

[@EEVblog]

Young whipper-snapper

[@aneeshprasobhan]

very useful . thankyou

[@Factory400]

Fantastic topic Dave! This is so relevant and useful. For those in need of some software try Wavdrom editor. Slick.

[@worroSfOretsevraH]

A nice follow up would be an introduction to reading through a more complex digital circuit made out of logic elements. For ex. a full adder or even something that has flip-flops mixed in.

[@GadgetUK164]

Great stuff Dave! Picked up a few new things from that =D

[@markpitt5248]

This is a great explanation, timing is a simple concept but when implemented gets complex very quickly. Its a case of seeing the wood for the trees, I look at some datasheet timing diagrams and my mind just panics! Knowing the very basics mean you can break it down into chunks and find the stuff that is relevant to you and what you want to achieve with a circuit.

[@EEVblog]

Thanks, and yep, that was the intention, breaking it down.

[@PHamster]

@5:33 OMG look at that jitter!

[@PHamster]

@Mai Mariarti That has the worst jitter in terms of clock generation

[@TKomoski]

Non buffered

[@electronic7979]

Helpful information. İ like it 👍

[@Schwuuuuup]

did anyone notice how many of Daves (fundamentals) videos start with a (lengthy) justification, why something should be understood? It's like the target group of those videos is a guy who just said "Nah, I don't read datasheets.... I just put some wires together and if it doesn't work, I'll call it a piece of crap.... Timing diagrams are just show off for fancy people"

[@EEVblog]

I never noticed.

[@Schwuuuuup]

@@EEVblog this was not a critique ... more concern what people surrounded you in your past ;-)

[@0xbenedikt]

@@EEVblog I like the intro. It makes sense to have it. Please keep it :-)

[@PyroRob69]

I remember drawing these back in the mid 80's when I was working with 8085's and all of the 74xx interfaces to it.

[@TheRokkis]

Heey nice! Tried to do some Arduino/shift register stuff a couple fo days ago, but the chip was "not the most common one everyone uses" and ShiftOut() was useless. After writing some code I realised I have no freaking idea what I'm doing, so your video is sooo valuable for me. Thank you for your effort, greatly appreciated!

[@EEVblog]

Good to hear, thanks.

[@msh6783]

thank you man

[@Tomabyte]

Hope this helps me with my microprocessors class

[@ftonello1]

Wow......finally someone did a tutorial about it!!!!!!.....thaaaannnk you so much !!!!!

[@crazyboy2006cashier]

I’m working on a z80 and have got quite far into it but this makes more sense

[@frankowalker4662]

I've got the Z80-Z80A Technical Manual from Zilog, dated September 1978. 75 pages of pure priceless heaven. Timing codes for every single instruction and state. Found it in a second hand book shop in the 80's.

[@crazyboy2006cashier]

Franko Walker a book of joy

[@dogastus]

This could do with a Part 2 describing pipelined logic comparing, say, hold time outputs of registers to setup times of succeeding registers. It's easy to violate these timings especially if you have long PCB traces. A trap is to feed high speed logic into low speed like a 74F logic feeding 74LS logic. Also, how to deal with meta-stability issues in asynchronous systems.

[@xotmatrix]

Yes, please.

[@uni-byte]

An important skill.

[@andyhello23]

Good video. These are things most out there totally ignore, in there teachings of electronics. I have never seen a vid on this before, so i assume this is not important to others whom teach. But nice vid. Once your in a system and educated to that system, you appreciate what you really need to know as a student. So nice vid.

[@jamisonw.327]

Dave, you should give Shenzen IO a try. It'd be funny to do a "let's play" but it actually has some quality engineering concepts to go through. I mention it here because the goal of the game is to match a data output signal using different chips and assembly language.

[@Jack-im2wd]

Silicon Zeroes is another one of the same vein that I enjoyed playing as well; both are worth a look!

[@jamisonw.327]

@@Jack-im2wd There's also a few phone games. The one that comes to mind the most is the sequence. I'll check the one you mentioned out too.

[@Electrodudimanche]

Like most here, I had to understand them on my own the hard way. Still not mastering the thing, but at least I can now read and understand them.

[@ionelvranceanu6413]

Some of them are a little bit hard to understand, but i've learned much more than in college

[@MatthewSuffidy]

Do devices have IMCs to connect to DDR without worrying about this? Are some bus devices designed to have compatible timings?

[@5Breaker]

Hi Dave, there's a game what might be also a good example for this. Shenzhen I/O. And Scott Manley has a nice play through.

[@marksteven3534]

Hi Dave, could I use my rolex oyster day-date to check the timing of the chip.

[@shkhamd]

Part 2 could be on how read those logic block diagrams like in 3:55. I have always had hard time interpreting those.

[@tablatronix]

yay! These always confuse the crap out of me especially when they have dual overlapping traces.

[@RealRobotZer0]

4:57 "come a gutter" what does that expression mean?

[@VK2GPU]

Timing diagrams are pretty similar to how I try show flow of data or distribution of workloads across multiple threads. Wish there was a standard way to do it, but in software engineering it seems to be the same "standard" approach - Whatever makes sense, mostly.

[@gudenau]

I feel like this is something that you need a decent scope or a logic analyzer for. One day I'll have to grab one, especially when I start using DRAM and FPGAs....

[@wpherigo1]

gudenau I think I understand where you are coming from, but logic analyzers don’t replace timing diagrams. Mostly, timing diagrams are mostly used in the design phase when you don’t have any hardware to use an LA on. They establish not only exactly how the chips work, but also what chips can be used together and what the line lengths need to be. The other thing is that LAs show you how something is working, not how it is supposed to work! It’s a great skill to acquire!

[@gudenau]

@@wpherigo1 I didn't express this thought too well. I meant debugging stuff with.

[@isacson]

I prefer the Phillips or NXP datasheets ✊

[@nikolaint]

Can you make video about transistor amplifiers with active(dynamic) load and how to calculate bias of transistors in this type of circuits?

[@PicaDelphon]

Perfect Timing..hehe..

[@Jimmeh_B]

TBH, I haven't tried to design anything complicated enough to require drawing a timing diagram since about '98. Or if I have, it's just worked through sheer luck. Not to say they're not important! It's critical to understand them, not just in the digital space either :)

[@buddyryanmckendrick6601]

Hi David. Ben Eater once explained a similar topic but i kinda didn't get it. Would it be to much asked if you could explain how to calculate the "pulse" time built with resistor / caps to use for WE (write enable) needed according to a time table? i want to use a push button to enable WE while i have already set the data x on adress x to save the data on a SRAM? a small schematic would be awesome and a simple to understand way how to calculate the pulse time (uF & R) Respectfully from Switzerland BRMc

[@reddcube]

Which is verbiage easier to understand Positive Edge or Rising Edge

[@Waccoon]

Man, it annoyed me to no end to find that some datasheets don't have the diagrams to scale. Thanks for mentioning that. I was having a hard time understanding what was going on with regards to page mode timing of some old 8-bit DRAM chips since the distances between the signals didn't match up with the numbers. The diagrams help to understand function, but always go by the numbers!

[@EEVblog]

Yeah, really annoying and confusing when you first encounter it

[@CaspaB]

For the benefit of those not up to "timing diagrams" but wanting something more basic, could you do a video about Karnaugh diagrams and Truth tables pls. Doh! #981

[@OmarMekkawy]

Nice video really. Could you show us how you did the bit banging on your episode #1000 for The TV text overlay device ( as an application for the timing diagram ? )

[@EEVblog]

That might be interesting.

[@OmarMekkawy]

@@EEVblog Thanks a lot.

[@tuttocrafting]

I would love to see a complete video on how to properly analyze a circuit, understand how it works and why. BTW, I'm not talking of simple Kirchoff laws applied to resistors. Maybe something with op amps and or discrete transistors or diodes. (At school I've studied only some parts of electronics and so far I cannot understand how transistors works in a circuit. And yes I have read lots of different textbook but I think that I miss something quite basilar)

[@EEVblog]

You can't just do a generic "analyse a circuit" tutorial. There are an infinite number of permutations on things to learn in even the most basic circuits. Each component requires it's own hour long video (see my 45min opamp video, and I didn't even cover everything), and then you could do another 1 hour video on interpreting datasheets and parameters for those components, and so down the rabbit hole it goes.

[@syrtismajorstudios2185]

A good basic introduction of how a transistor works in a circuit is to think of it like a dial or slider light switch in a room. One that changes how bright the light is. Except instead of using your hand to change the brightness of the light, a transistor uses a voltage applied to two of its pins (base and emiter). So if you put an ac signal such as a 1kHz sound sinewave on those two pins it would be like turning the light control up and down 1000 times per second. A transistor is basically a switch with its on/off state controlled by an applied voltage. It does not have to be full on or full off. It can be a little bit on with a small base emitter voltage wich would essentially be a high value resistor between the collector and emitter. Or it can be full on with a higher vbe wich would make the collector/emitter a low value resistor. It can also be anywhere in between.

[@devonmagan5046]

An easier way to understand a NPN BJT is by representing it by a water tap. Opening the tap represents the base, the main reservoir represents the collector, the water coming out of the tap represents the base and the water represents the current flow. When you open the tap the more current/water is allowed to flow. Eventually you going to open the tap to a point where there is no more change in water/current flow. This state is known as saturation. You can keep opening the tap and you will notice no change in water/current flow. Closing the tap fully is known as cutoff where no water/current is allowed to flow. The above applications would be switches. A BJT can also operate in other "modes". So when you adjust the tap between saturation/opened a lot and cutoff/closed and see a direct change in the water/current flow, this is known as the active region. This "mode" has many applications for example amplifiers. Just a simple way to maybe grasp a few Concepts.

[@tuttocrafting]

@@EEVblog yea, I know that the permutations are a lot. With "complete video" I means to take a schematic and analyze it trying to teach the method to understand how a circuit could work. For example divide the circuit into blocks, find the inputs and outputs. Use Kirchoff to calculate the current and voltage drops. I have lots of notes from my old electronic professor, circuits to analyze that have also diodes in them. But he never explained how to apply the rules of Thévening or Kirchoff in thoose cases. Our electronic program was: bool logic, resistor based DC circuits, logic gates. Then we switched to AC, Bode and Fourier application. Op Amp. DAC and ADC, S/H and a basic signal processing theory for sensors.

[@tuttocrafting]

@@devonmagan5046 Thanks for the quick notions about BJTs. But I Known that. The problem is properly analyze the circuit. I've seen different schematic of amps made out a couple not BJTs but mostly black magic for me. Use transistors as switches is not that hard. I've done fire experiments with them. But so far I'm not completely able to use them in the linear region. To properly create a load or amplify a signal. Opamps are "easier" for me since I've studied them properly!

[@CaspaB]

I don't believe in frequencies above my audio threshold ( DC to 12 kHz ) so reading timing diagrams is easier. ;-) I'm stuck in the 1980's (CMOS, TTL) era

[@IsaacMorton]

You can hear DC? Impressive!

[@martinda7446]

DC? What sort of ears you got? 📢🎤🔉🔈🔔🎼🎵🎶🎷🎺🪕🎻🎧🍄🌶🥒

[@CaspaB]

@@IsaacMorton Nearly DC. About 0.1 Hz. You get it by slowly pushing a screwdriver into your ear. Stop when you hear or feel a "pop" as your eardrum bursts.

[@martinda7446]

@@IsaacMorton Ha, ha you weren't there a moment ago? I was playing silly buggers with those emojis....Took a couple of minutes..Means we wrote our comments exactly the same time.

[@williamsquires3070]

Um, Dave, you missed it again. The timing diagram for the TI chip clearly shows at the bottom, that the cross-hatched areas are tristate mode. Doh! No need to go to the schematic or block diagram. Although you can, if you really want to! 😏

[@EEVblog]

Keep watching, I commented on that.

[@dfl4m]

For those how want to draw timing diagrams there is an open source program for this wavedrom.com/

[@Newbrict]

What is OE in the 23:31 - 27:00 examples?

[@benhetland576]

Probably Output Enable (active low in this case) after you have read a few of those diagrams, but most likely you'll find it explained somewhere else in that document.

[@gryzman]

Dave, Dave! Look at notes below the diagram clearly showing 3-state. Just like with australian EVs and Tesla, world is a bit more nuanced than you want :-)

[@EEVblog]

I commented on that, keep watching

[@nickname1392]

How good are you at understanding DRAM timings?

[@rethinkscience8454]

Can you do a show about the Mobil phone. Does it still transmit location when turned off and is their un reported transmitter running on different frequencies

[@teabone30]

WaveDrom is a nice text based editor for creating timing diagrams: wavedrom.com/

[@leoramikam1051]

Can you please help me with this diagram? I am trying to drive a VFD display I got. Using arduino library for esp32. there is an 8-bit parallel data interface I am trying to write to. You can please see the timing diagram here - imgur.com/a/hnzC69y . Based on that, I tried the following code sequence, but does not seem to work. I know the display works because I can put it in test mode. Does the code look correct against the timing diagram? thanks! digitalWrite(PIN_CS,0); delay(1); digitalWrite(PIN_WRITE,0); delay(1); digitalWrite(PIN_B0,0); digitalWrite(PIN_B1,1); digitalWrite(PIN_B2,0); digitalWrite(PIN_B3,1); digitalWrite(PIN_B4,0); digitalWrite(PIN_B5,0); digitalWrite(PIN_B6,0); digitalWrite(PIN_B7,0); digitalWrite(PIN_WRITE,1); delay(1); digitalWrite(PIN_CS,1);

[@aneeshprasobhan]

why does the audio sound wierd ?

[@EEVblog]

How so? Anyone else?

[@frankowalker4662]

Well it's about time!!! No appologies at all! Ha Ha!

[@SurajGrewal]

10:13 all sorts of weird and WONDERFUL problems 😂🤣 ROFL. No thank you.. I'd rather have my project working on first try

[@EEVblog]

No, you don't, trust me. You learn nothing from a circuit that works first time.

[@LifeofanElectronicEngineer]

If you ever want to draw timing diagrams, this software is perfect! wavedrom.com/ EDIT: and free!

[@gapadad2]

AT 8:35 I REALIZE I'M NOT WATCHING THE REST OF THIS VIDEO

[@pahom2]

25:50 I don't like the phillips middle line representation of a z state at all. This imply that the level is in the center and neither low nor high, while it can be red low or high in any point in time during the period. The greyed rectangle is much better showing that the level is undetermined. Thumbs down to phillips, that is NOT how you do it.

[@EEVblog]

Sorry, I disagree. It very clearly illustrates that the chip is no longer driving that pin.

[@pahom2]

Or drive it to the middle point. Right? There are so many options how to image z state. Grey rectangle, dotted low and high lines at the same time, curved line or even the lack of line, but the straight line going through the middle between high and low is the worst possible illustration.

[@EEVblog]

No chip drives it to the mid rail, that's silly to even suggest.

[@pahom2]

Yep. It is silly that phillips suggest that the output level is in the middle and not high nor low. A grayed rectangle better represents the voltage level indeterminism here, and no beginner would even think that the level can't be red low during the period. The other question is how to represent x state i.e. active drive to random value that can't be pulled with a resistor on the same diagram with z state. But pulling the z state would require a more detailed description anyway.

[@DAVIDGREGORYKERR]

Slew Rate.

[@stryderpreside]

Very smart man with an annoying voice and a bad attitude. Can’t deal with him.

[@Mriks007]

I think your audience is more professional, why do you talk like you're talking to a beginners audience? I think better way to explain this is to make simple demonstrate talking micro with any 74hc599 and writing some c code . . .

[@sonnywilliams6566]

This reminds me of Know More New's video about November 3rd.

[@sonnywilliams6566]

When are we gonna see the uFarting Novelty Gadget?

[@EEVblog]

Coming soon, but it's hard to get the smell right.