Clock (and I guess other signals) waveforms

[BigDumbDinosaur]

adrianhudson wrote:

BigEd wrote:

(Sorry - I think you'd be better off looking into resources like electronics stackexchange, rather than have me write an essay. In my opinion, it's well worth the journey of trying to understand electronics, and you have some of the gear to help you. But you will need to do the work - you need to build a mental model and you need to have some terminology to hand. Good luck!)

Well thanks for that
I really apologise. I wasn't aware there was a limit to the type of question allowed here. I thought this was a newbie forum where people trying to learn stuff came to ask questions. Sorry

There is no limit, other than the limit of practicality.

Digital circuit design is a vast topic on which literally hundreds of books have been written and countless technical articles have published in magazines and on-line. It’s much too vast to even start to explain in some forum posts. Also, it’s one thing to have the requisite knowledge, but quite another to successfully articulate it so the newbie will understand. The website Ed suggested has a ton of information that has already been organized and (we hope!) fact-checked. It would be a not-insignificant undertaking to repeat even part of it here.

Newbie questions are certainly welcomed and encouraged—we want you to experience success when you power up your new contraption for the first time. At the same time, we encourage you to take advantage of the vast amount of information on the web. Sites that have digital circuit design info will do much more for you than merely tell you what to do or not do. Most of them will also explain the theory that is essential to know if you are going to have a lot more successes than failures.

A good place to start is at Garth’s website, which goes from A to Z in designing a 6502-based system. He also discusses programming in articles such as his interrupt primer. Garth’s site isn't exhaustive, but is perhaps the best independent collection of 6502-oriented info on the web.

[BigEd]

Indeed so, thanks BillO and BDD for saying more. There are several of us here - perhaps even many of us - who are more than happy to help someone along step by step as they pursue their 6502 project, be it hardware or software.

And it might even be that if someone asks for a grounding on some general electronics topic, someone will have the energy and generosity to write some paragraphs.

But note that very many such questions have been asked before - there's a great wealth of such Q&A already on the forum. And the forum has a search function! And many times, you'll find the answers will link to excellent resources elsewhere on the web.

So, in this case, and in other cases, I ask that the newbie should put in at least as much effort as they are asking me to put in. It would be a good sign to hear "I am still confused about X. I have read Y and Z and I think the story should be A, but observation B still has me puzzled."

Above, we're all people - both the newbie and the old hand. We all have other calls on our time and energy. This forum is not an oracle - it's a way to reach people and for people to help each other.

[BillO]

BigDumbDinosaur wrote:

CountChocula wrote:

My understanding is what drives a lot of noise and ringing in digital signals is the rate at which a line switches from one state to another...

BillO wrote:

For instance, the can oscillator might only be a 1MHz frequency, but that is just the clock rate. The leading and trailing edges of the pulses rise and fall at a rate that could represent frequencies in the 100s of MHz range.

Funny how everyone is repeating what I earlier posted.

It's just that it's worth repeating.

[GARTHWILSON]

The forum's search can be a little frustrating at times, and it often tells me it won't search for certain words because they're too common, which they're not, or if they are, it's an exact phrase I remember and want, words in this exact order, but it only searches for the words it will accept, regardless of their order. Edit: I wish search engines had an option for case-sensitivity. Sometimes it would make the difference between 30,000 search results and only three search results!

For the newbie, the many pages of results of even a successful search can be overwhelming. There's a ton of material here, and Sheep64 may be the only one who has read the entire forum, and it took him many months. (I do at least scan everything, but that's not the same as thinking everything through.) Newbies do well to say something like, "I've done A, B, and C in my effort to understand my problem, but I'm still stumped. You've probably discussed this at length before, so I hope you can just direct me to a good thread" (which we often do anyway). It might even remind someone of an old topic that could use an update now that more has been learned or a better component or new resource has become available. So often however, we spot a potential problem the newbie is still blind to, and we (myself included) seem to lack the communication skill to get him out of his tunnelvision. (I'm speaking generally, not particularly about Adrian.)

AndersNielsen in his video recently said I seem to have inexhaustible patience to help newbies. My enthusiasm about promoting our interest may have an irrational component to it (LOL); but my patience does have its limits. I have to remember we were all beginners at some point (and we're all still learning), and if we want to get some new blood into this field, we'll have to show the same patience with the newbies that someone may have shown us way back when. (One thing I don't have the patience for is reading schematics that are really just a netlist written around boxes, with a ton of tags that we have to search to match up.) I initially wrote the 6502 primer to answer questions and problems that kept coming up on the forum; and I keep updating it regularly as new questions show that I failed to address something, or that something in the primer either isn't clear or it's too easy to miss, or I myself have learned more since I wrote it. (Thanks for the compliment, BDD!) It does take a lot of time; but once something is on the site, it's easier to give a link than pound it all out again and again.

I keep thinking I should have a web page on circuits that don't relate directly to 65xx but do have to do with powering it (like switching-regulator circuits), troubleshooting it (like the short-finder I posted recently), signal conditioning for A/D and D/A converters (like anti-alias filters), sensing, tape modems, and more. This forum could use a lot of help in basic DC circuit analysis, basic AC circuit analysis, and basic transistor theory.

[BigEd]

I'd quite like to write the essay that I think is needed to address Adrian's queries upthread, but I haven't found the energy.

It's possible that we'd all be better off if I hadn't responded, but left the questions to someone who did have the time and energy (and expertise) - I was wrong-footed by being directly addressed, and perhaps not in the best of moods. Again, sorry. I do want this forum to be welcoming and helpful - I also want it to stand as a searchable resource of good advice. Sometimes a websearch targetting the forum will do better than a forum search.

There might also possibly be a cultural element in play: in chat applications, from IRC onward, one expects not to read reams of backstory, and one expects a to-and-fro of conversation. In a forum, for me, the approach is more bookish than that. More people these days are used to the quick response as opposed to the studied reply. That's fine, but it's not my preferred approach for deeper technical questions.

I think I've mentioned before the idea that electronics is not like Lego - it's more like building a model aircraft from paper and balsa wood. If you follow instructions you might get something working, but in the case that something doesn't work, there are potentially lots of subtleties in play which might be the cause. If you can find the right materials and take a studious approach, you can come to a deeper practical understanding and ultimately be able to build your own designs.

[adrianhudson]

I'm not quite sure how to respond - or even if I need to respond to the preceding posts. There is no need for anyone to apologise to me - however, since it has been done then I should respond to accept it. In comparison to MANY other forums I have visited, this forum seems to be populated by exceedingly polite and considerate people. Okay, that subject closed.

I will heartily agree on the forum search. Why forum software can't be written to accept "cleverer" search terms with quoted string and logical comparisons I really don't know. So much valuable info is locked up in these places and yet finding it can be frustrating to say the least. Some people might not be aware so I will mention it here that Google searches can be qualified with "site:forum.6502.org" (no quotes), so to expand on BigEd's commect of using external search engines, the Google search "foo AND bar site:forum.6502.org" (again those are my quotes) for example with search for posts containing foo and bar. The internal search, when asked to find foo AND bar would return any posts with "foo" or "and" or "bar".

GARTHWILSON wrote:

I keep thinking I should have a web page on circuits that don't relate directly to 65xx but do have to do with powering it (like switching-regulator circuits), troubleshooting it (like the short-finder I posted recently), signal conditioning for A/D and D/A converters (like anti-alias filters), sensing, tape modems, and more. This forum could use a lot of help in basic DC circuit analysis, basic AC circuit analysis, and basic transistor theory.

Garth, those would be a wonderful additions. I appreciate it would be a lot of work but the wealth of information in your primers is fantastic and would be even better with even some of the subjects you mention - power supplies and troubleshooting especially.

[BigEd]

Cheers Adrian - no worries, I'm not seeking anything here, just mumbling about what I'd quite like to do if I had the energy, and was never grumpy!

(Sorry, all of this has veered a bit from the topic, but I'm finding it interesting so I'll keep going...)

Quote:

Google search "foo AND bar site:forum.6502.org" (again those are my quotes) for example with search for posts containing foo and bar. The internal search, when asked to find foo AND bar would return any posts with "foo" or "and" or "bar".

Indeed, I use "site:" really very often. (I believe you don't need the AND with Google, although over time they have become increasingly fuzzy. I know some search facilities assume OR, but these days I find most of them assume AND - which to my mind is the right way to go.)

Someone mentioned the other day that the Stardot forum assumes OR - and I was surprised, as I was surprised right here and now, because in my experience both Stardot and this forum will assume AND when I search for multiple words.

(For example, "wonderful additions" presently finds only a single match, here, although once I've posted this it will probably be two matches. Whereas, "wonderful" finds 249 and "additions" finds 207.)

Maybe for some people the preference in search is set to "Search for any terms" whereas for me it's set to "Search for all terms or use query as entered". Maybe in the distant past I changed it, and that's why I'm seeing different behaviour?

I too find that stop words(*) in forum search can be a hindrance... although right now I can't seem to find any - even "the" is not too common to be a valid word. Maybe Mike tweaked the forum to be more generous?

One final tip from me on search: the forum search will allow limited wildcards, so "board*" will match both "board" and "boards".

(*) "The following words in your search query were ignored because they are too common words:"

[BigDumbDinosaur]

BigEd wrote:

I'd quite like to write the essay that I think is needed to address Adrian's queries upthread, but I haven't found the energy.

In some of my posts in which I describe things on which I am working, I include some theory in the hopes the reader will better understand what’s going on. Providing the “why” as well as the “how” makes things more informative and interesting.

That said, technical writing of any kind tends to be very time-consuming. Like Ed, I am increasingly having trouble mustering the energy need to write about technical stuff in a lucid fashion. I’ve often wanted to write a programming manual for the 65C816 that exclusively focuses on the MPU operating in its native mode and is targeted to an audience that is interested advanced programming techniques. Wishing, unfortunately, doesn’t make it so and the reality is that with me being in my late seventies and in failing health, I can’t justify the time it would take.

As we’ve said, scouring the Web is the best way to find the theory you need to know to develop good designs. There’s quite a bit here, of course, but searching is not a strong suit of the forum software. Ed’s suggestion of a targeted Google search would help in that regard, although I tend to discourage the use of Google’s search engine, for well-known reasons.

[drfiemost]

I haven't seen this mentioned but a square wave is a sum of infinite sinusoidal harmonics which can't be represented correctly when sampling, so you end up with a bandlimited signal affected by ringing and overshooting. See the Gibbs phenomenon

[JimBoyd]

GARTHWILSON wrote:

The forum's search can be a little frustrating at times, and it often tells me it won't search for certain words because they're too common, which they're not, or if they are, it's an exact phrase I remember and want, words in this exact order, but it only searches for the words it will accept, regardless of their order.

I've been annoyed by that. It would be nice if a search term was in quotes, every character in the quotes had to match exactly, including punctuation and spaces.

[BillO]

adrianhudson wrote:

I will heartily agree on the forum search. Why forum software can't be written to accept "cleverer" search terms with quoted string and logical comparisons I really don't know

I agree. The search feature is abominable. However, it's not easy to write a good one. Especially for software like this which is: A) free, B) intended for general use.

I don't mind patting my own back here but I have written search engines that would put 6502.org to shame. HowEVer, let me stress some things.
I's not just a simple matter of making an easy to use yet incredibly powerful UI that takes in anything people enter then makes near perfect sense of it (details would take pages), but you must first be able to index the searched data properly too. That means (simplistically speaking) one of two things: 1) Have extensive expertise in the subject matter that will be searched, or 2) a) spend a medium sized fortune on a self-learning indexing algorithm that will figure out for itself how the subject matter at hand is trending, and b) identify and profile search indexes on a per-user basis.

Option 1) is a less costly(but definitely not free) alternative, but is of limited applicability in a general use product. Option 2) cannot reasonably be accomplished in a product that is free and supposed to run on equipment that has a low maintenance cost.

We have this, which is cheap and cheerful and does not require a warehouse full of servers and 10 petabytes of storage to implement, then we have Google that is an example of option 2 a) and b).

I have created systems that meet option 1) criteria but it took a team of 5 two years to complete at an average salary of $80K/year back in the mid 1990's. It was friggin' slick tho! AFAIK is still in use today.

[BigEd]

Let's not bite the hand that feeds us. This forum is a phpbb instance, and it offers features accordingly.

I've been unable to find any stop words - are we sure that 'this term is too common' still comes up in practice? I can search for 6502 here and get 30k matches.

As with other phpbb forums, I do commonly use my preferred search engine to find site-specific results, and I can even use time bounds to find what I want.

[Sheep64]

GARTHWILSON on Mon 27 Jun 2022 wrote:

Sheep64 may be the only one who has read the entire forum

I'm the only person who has admitted it. I estimate that four or more lurkers have read the entire forum. Actually, after reading pagetable.com and anycpu.org, I planned to read an Acorn forum, an Atari forum and a Commodore forum. I may be rare but I cannot be the only person who reads everything on a website.

GARTHWILSON on Mon 27 Jun 2022 wrote:

I do at least scan everything, but that's not the same as thinking everything through.

I de-duplicate all text before reading with text-to-speech. This eliminates all of the quoted text. Unfortunately, it greatly truncates memory maps and program listings. With or without truncation, some of the Forth is incomprehensible and I cannot exclude the possibility that it may be a game akin to Mornington Crescent.