I always turn of adblocker when watching Daves channel. He deserves every penny he earns.

wow! I have been using JTAG for programming for many years and I never realized about its true power until I saw this video! great work my friend!!!

I am software engineer with passion on hardware, used JTAG and ICE 10 years to bring up few products with fresh hw engrs passion on sw. We did. Now, the way you explaining things artistically can make any one understand and get motivated. Wow! Keep going for all.

I realised that I wasted a whole day just theoritically googling to understand the jtag/boundary scan concept until I saw this video of yours

We used JTAG to control uC. I never knew the "boundary scan" feature exists. Thank you for explaining the wonders of JTAG!

I have been working with electronics for a while, i have been hearing my colleagues using the word 'JTAG'... never knew what it meant or how it is used. this video was a great eye opener. words fall to short to describe the gratitude i have for such an insightful video thanks a million... keep up the good work man

Why did not I has a video like this when I was in the college? Save a lot of effort in understanding JTAG.

One of the best (if not the best) explanation of JTAG and Boundary Scanning that I've seen. Good stuff.

EEVblog Thank you so much for these videos! As an engineering student with a lot of interest in electronics, I have been watching your videos quite often, and always learn something new! Thanks again Dave!

@AvstoMusic - Each JTAG pin "site" knows whether it's an input or not, so an input won't 'adopt' its shifted-in value. Instead, it will ignore the shifted-in value and shift out its current value - when TMS is strobed, at least! So a host performs a complete scan by: [1] Shifting N bit values; [2] Strobe TMS to "Make It So!" (see my previous comment); [3] Shifting N bit values. That will program the outputs to the desired values, and then read the resultant values.

You probably dont have time to read comments but you inspired me many years ago. I used to watch your videos knowing very little about this stuff. Today I'm repairing boards of all natures, doing trace repairs, and I've recently had to repair a completely snapped board. I was a software hacker, and hardware just seemed like the ultimate way to control and manipulate hardware. During my time hardware hacking I invested in a good stereo microscope, oscilloscope and rework station. I had all the tools to do repairs, so now I do that because it's good money, more fun, and beats my old programming career. Thank you :D

Thought JTAG was difficult But you forced me to change my mind. Thank you very much

You are better than the best professor at my college. Great video. Keep up the great work. The electronics world needs more people like you!

dude !!! you are soo good in presenting what is on your mind i like what you are doing a lot thank you so much for the valuable information and good demos !

Wow, I normally have a difficult time understanding hardware related stuff, but you explain it like it was basic. It takes an expert to explain difficult stuff easy. You nailed it, subscribed.

This was an excellent explanation about JTAG and boundary scan. This video is very clear and can be understated by any electronics graduates. It helped me a lot to understand the uses of JTAG and boundary scan in FPGA. Thank you sir:-)

Such an amazing information. We have been trying to debug faulty PCB's since 1 month and now I got a wonderful tool to utilise. Thanks a ton!

Wow! This was a great video! And thanks for showing the software at the end... it gave some examples of how useful JTAG can be.

Nobody can equal Dave when explaining difficult subjects like this and make them easy to understand!

Fascinating Dave, thanks. I'm using JTAG for flash and debug on my ESP32, but it's great to know of all of the extra power behind JTAG.

Thanks for making it so simple and easy to understand the concepts of JTAG

The real beauty of that xjtag system is that you can write code that describes how to test a particular chip. Once that's written, anytime you use the same chip on any of your boards you can call the same test routines. So it hides all the serial details from the user and makes your test routines very reusable. I loved it when I was doing test.

Very thorough, very clear descriptions. Thank you so much!

Found it in 2022. This is an amazingly clear explanation! Thank you so much. Really helps one understand what the heck JTAG is.

This is awesome! Perfect video for a beginner in Large-scale industrial chip design

Amazing! A video with theory explanation and with a practical example!

Awesome video really couldn't have made this more clear.

Wow. I was just reading an introduction to JTAG's interface and its implementation like the TAP controller state machine. Great timing with the video, Dave. It really complemented what I just learned. Now I got a JTAG itch to go scratch :)

Thanks Dave , I didn't know about the boundary scan possibility with JTAG only the programming functions. This was a great eye opener for me!! Cheers!

Thanks for this video! I had no idea JTAG's capabilities went that far, I always thought it was just for flashing chips and debugging your programs. Wow! I could see the direct pin access being very useful in a production environment for doing electrical tests on finished boards. Very nice, keep up the cool videos!

Really helpful video. You explained it very well and I got to know a lot about JTAG. Thank you very much

My university professors need to follow this channel. Full of knowledge, full of respect Dave. Thanks!

Way late to the party here, but I see JTAG on just about every product I test at work. Much appreciated information on this. Great video!

You seemed to gloss over the fourth JTAG pin: TMS. Your description of TDI, TDO and TCK were perfect - but think about what would happen if they were the only pins, and TCK shifted the 1s and 0s through all the different pins... There'd be chaos as the differing values produced different results! That's what TMS is for. Think of it as Jean-Luc Picard saying "Make it so!" - until TMS is used (I think of it as "Master Strobe"), the shift registers just shift the data. TMS is used to "latch" the current state into the actual pins.

Yeah, I'm going to need a direct JTAG interface into your brain.... Your ability to break complex things down simply is unparalleled in my opinion, and I greatly desire that ability.

Thanks so much for the explanation. Very helpful and very well made

I always use the lapel mic for recording FF video, I have to, as the camera is 3 meters away. But when shooting on the bench I use the internal mic. Lapel mics are not perfect, and if you turn your head the volume varies a lot. I passed this one through The Levelator to level out the audio, which is not easy to do in my Sony video editing software.

Very good. Thanks. Just to remind that signal integrity should be taken into account carefully. If many chips with JTAG pins exist, say complex boards, I prefer using CPLD to access each chip directly rather than having chains (chains can be established on CPLD rathher than PCB with maximum flexibility) and installing/uninstalling jumpers on TDI-TDO pins. And of course optional TRST pin exists as well.

That was so interesting and powerful protocol thanks Mr. David 😍😍

Good video. I'm more involved in software but wanted to learn a bit about JTAG and this video was a really good introduction for me. Thanks

Amazing tutorial thanks!

Great Vid! This complements nicely with my knowledge of using JTAG to flash routers, really opens my mind and makes perfect sense

I initially thought that JTAG was for testing purposes only, like hardware faults and cold solder joints and such. But thanks to Dave, I now know how powerful it actually is at performing many other useful things like programming chips ! And all of that in only 29 minutes ! (actually 20 minutes because I watch the video at 1.5 speed)

You are awesome, so glad I stumbled upon this vid!!!

Dave KZfaq University.. you are a very good lecturer

Am I alone losing my eyesight by constantly watching Dave's amazing videos?

Dave has such a soft and calming voice in this unlike his later videos.

You got to love the enthousiasm !!! Love the content.

Dave, these videos are awesome, I will go back and watch all you have made.

I really enjoyed this one! Thank you Dave!

Fully expected my brain to fry and scream "mercy" but this was in fact easy to follow and enjoyable to the last. Thank you Dave!

Well yes, of course you need good software to decode all display the info, otherwise you are just looking at The Matrix

Used to work with JTAG and Boundary Scan. Went on a course in the Netherlands with Eindhoven.

Excellent explanation of 1149.1 Boundary Scan, but if the green rectangles represent your I/O driver & receiver ckts, then I would have drawn the the green rectangles outside of the blue ones. The output test data is fed into the drivers by scanning it into the boundary scan latches and then driven off-chip. The receivers conversely receive input test data from off-chip and feed it into the boundary scan latches, where it is captured and scanned out. As drawn, this diagram implies that latching occurs between I/O ckts and the physical chip pin.

I didn't know it was used for programming, i did know it was used for testing and debugging but I never knew how it operated. Very informative video.

Thank you very much for all the Explanations and videos you make ... God bless you

Excellent video Dave. Reminds me of the Engineers access method for diagnostics on ICL 2960 mainframe computers. We could access all the registers of the system by " spinning the loops" and read the contents of all the registers on a serial bus. Keep up the fundamentals Friday stuff. Maybe some more novice vids would be good?

You are what my college needs. Hats off to you.

can i please copy and paste your knowledge into my brain?

Really good one. Definitely turned me on to possibilities of JTAG.

That was very useful and interesting. Thanks for this Dave!

Hey Dave! Thank you! That was very informative

Great video Dave - A few things were repeated a little too much, (that's what rewind is for) but overall: really interesting and educational. Thanks!

Excellent , Dave. Thank you.

Very good video. I am just a hobbyist, but it is good to know that the 'big boys' need to debug pin by pin also.

Non ti abbattere, la maggior parte dei discorsi sono semplici da capire soprattutto perché con il video si riesce a raffigurare quello che spiega e tu puoi associarlo al discorso.. Guarda anche altri suoi video e piano piano avrai l' orecchio per seguire tutto quello che dice :) Ciao

Great video! I was not aware that you could read and WRITE pins directly via boundry scan.

Thanks for this fun intro to JTAG, Dave.

Very much clear description!!!! Thanks!!

We now need a video about IEEE Std 1149.7 which is only a 2-wire interface.

Great presentation. Very informative. Many Thanks.

oh i am 100% playing with this in my next project this is so cool

Amazing, thank you so much for this!

very good explanation!

Hi ! Always enjoy watching the videos ;) Just had a Suggestion ... You know , the content is just great ! but those huge length of episodes really give me a second thought :)

great video Dave, thank you.

Excellent, Thank you very much Dave

Thanks, this was useful for learning

Loving these fundamentals videos!

Great video! Clear and concise. Liked and subscribed

Very Good explanation!. It was very very useful

Excellent video Dave. Thanks very much!

This is very informative. Thank you for the video

waaah thank you so much ! this is really well explain and definitly usefull !

I remember the days we were doing joint test action, not much real work was done afterwards...

Thanks for the video Dave, I love Fundamentals Friday!

I learned a lot thanks to this video... thanks Dave

this is exactly how i wished to be explained! i loved it

Simply wonderful ... Great ..you deserves allot...

This is awesome it's been around that long

That was really helpful.. You are amazing.. Thanks!

woow .. Awesome Explanation ..Thank you

Thanks for doing these Fundamental Fridays. Opposite to most people, but I prefer these to the dumpster diving and mailbag videos even if I already know the content.

Awesome, as always! thanks dave.

Dave, you are the freaki'n best! When I get some money I'm going to send you a donation - you deserve it.

Very nice and exciting. Thanks.

Cool explanation for start.

Great description - thanks

Can we load test vector patterns to the chips via JTAG Boundary Scan and read the output and compare it with known output pattern wit this XJ-TAG tool.

absolutely amazing! thank you!