Crystal Oscillators

[GARTHWILSON]

See http://en.wikipedia.org/wiki/Crystal_oscillator . There will be a tiny difference in frequency between the parallel resonance and the series resonance. If you get the wrong one, it will still work, but the frequency will be slightly off. "HC49U" is a common crystal case size. You can look at the choices in big distributors' catalogs, like this one of Mouser. (It's page 1 of over 100 choices!) My 6502 primer's page on clock generation is http://wilsonminesco.com/6502primer/ClkGen.html . It has links to some ap. notes also.

[BigDumbDinosaur]

LGB wrote:

Hi, maybe not the best topic to ask, and maybe not the right forum ... It seems I have lack of knowledge about quartz crystals.

Could you describe your intended application? It may be that a TTL can oscillator will be suitable. Can oscillators are readily adapted to most circuits and relieve you of having to work out crystal implementation.

[LGB]

Well, I mean about a crystal alone, not a can oscillator. I am sure it's because the lack of the knowledge at my side, just I have problems to understand the situation. If you see a schematic, you can read that eg you need a "BC 107" transistor, so you know the exact type. At the other hand, when quartz crystal is shown only the needed frequency is shown not the exact type, if parallel or serial crystal needed etc, it's like with transistors where it would be shown only "NPN/PNP bipolar transistor with ..." written and not the exact type. So I have the problem not with a single application but in general with any project/schematic shows a crystal but no more detailed information what type I would need ... Even on the site of mouser, only frequency and similar things are shown in the tables but not the parallel/serial stuff ... So I don't know how I will know which I need to buy. Maybe I should go with can crystal oscillators instead of lone crystals, however it seems they haven't got the same large selection of frequencies as crystals have.

I am not sure if my English is good enough to be able to describe my problem in an understandable way though. Thanks for the answers.

[GARTHWILSON]

On Mouser's site, if you click on one of the stock numbers, you'll get a page that's just about that one crystal, and there will be a thing to click on for the data sheet for it. I looked at a few, and it looks like they're parallel if they specify a load capacitance, otherwise they're series. It would still be good to look into it further. Going to the websites of the various manufacturers will probably give you the needed education on the subject.

[LGB]

GARTHWILSON wrote:

On Mouser's site, if you click on one of the stock numbers, you'll get a page that's just about that one crystal, and there will be a thing to click on for the data sheet for it. I looked at a few, and it looks like they're parallel if they specify a load capacitance, otherwise they're series. It would still be good to look into it further. Going to the websites of the various manufacturers will probably give you the needed education on the subject.

Ok, thanks. My only problem that I don't buy at mouser from Hungary (would be quite expensive because of tax and shipping as well) and usual Hungarian shops & webshops has nothing about "simplier" parts than only the name and some code (eg: crystal 12MHz) usually in "tall" and "short" package version in case of through hole. Anyway I don't want to flood the forum with my problems like this, I will buy both and I'll see Thanks again.

[GARTHWILSON]

Again, the frequency error from getting the wrong one will be very small. If you have a way to measure the resulting frequency, you can probably compensate in software if your application is that critical. For example, setting up T1 of VIA1 on my workbench computer for a 10ms time-out at 5MHz for a software RTC, I write $C34E to T1CH and CL. If I needed it really exact, I could, without even using a frequency counter, see how many seconds per day or per week that it gets ahead or behind, and adjust that number to compensate.

[BigDumbDinosaur]

LGB wrote:

Ok, thanks. My only problem that I don't buy at mouser from Hungary (would be quite expensive because of tax and shipping as well) and usual Hungarian shops & webshops has nothing about "simplier" parts than only the name and some code (eg: crystal 12MHz) usually in "tall" and "short" package version in case of through hole. Anyway I don't want to flood the forum with my problems like this, I will buy both and I'll see Thanks again.

Even if you don't purchase from Mouser, Digi-Key or other USA distributors, you can still use them as a resource for data sheets. The data sheets are free for the downloading and generally give you everything you need to know to use the product. If there is something that you don't understand please post about it and we'll try offer clarification. There is a lot of expertise here on many different aspects of computing, so it's likely that someone can offer explanations on what you need to know.

As I earlier suggested, you can help us to help you by trying to describe what you want to do. Sometimes it's best to describe your objectives rather than immediately dive into details. Don't worry about the quality of your English. I'm not having much difficulty understanding you, and I suspect others here won't as well.

[GARTHWILSON]

Mouser has branches in other countries too. I expect they're not the only ones.

[barrym95838]

BigDumbDinosaur wrote:

... As I earlier suggested, you can help us to help you by trying to describe what you want to do. Sometimes it's best to describe your objectives rather than immediately dive into details. Don't worry about the quality of your English. I'm not having much difficulty understanding you, and I suspect others here won't as well.

I agree 100%. Your English is very readable, and quite acceptable. Share with us what you're trying to do, and I can almost guarantee that someone here will have a polite and competent response. We're not here to give you a hard time ... this isn't Usenet!

Mike

[BigDumbDinosaur]

barrym95838 wrote:

I agree 100%. Your English is very readable, and quite acceptable.

Huh, Mike? I can't understand you.