help me to read acode on crystal oscillator

[fs789]

hi,
i have acrystal oscillator ,typed on its surface, the following:
20-480
HCJ-9-3
10-90
please,how can i determine the frequency of this crystal??
and ,when i use apic(for example 16f84a) for producing acertain delay time, can i achieve
better accuracy of time when using acrystal of high frequency ,i.e 10 MHZ?

 

[AtomSoft]

Maybe OSC 20.480MHZ

 

[RMMM]

HCJ is the manufacturer.
It is 20.480MHz
10-90 is likely the manufacture date. (October 1990)

IF you are deriving another frequency from an oscillator,it is best when you can do an even divide.

For instance if you want 5mhz, you would rather use a 10mhz and a flip flop than a 12mhz and software.

Look at a list of multiples for the frequency you WANT. Find the resulting product that is the closest match for what you have, or can get for you crystal budget.

If you have the money, consider having a crystal cut to order.

 

[fs789]

HCJ is the manufacturer.
It is 20.480MHz
10-90 is likely the manufacture date. (October 1990)

IF you are deriving another frequency from an oscillator,it is best when you can do an even divide.

For instance if you want 5mhz, you would rather use a 10mhz and a flip flop than a 12mhz and software.

Look at a list of multiples for the frequency you WANT. Find the resulting product that is the closest match for what you have, or can get for you crystal budget.

If you have the money, consider having a crystal cut to order.

thank you very much.
But,my question is, is there any relationship between accuracy of delay time AND FREQUENCY OF CRYSTAL??

 

[RMMM]

thank you very much.
But,my question is, is there any relationship between accuracy of delay time AND FREQUENCY OF CRYSTAL??

Yes. The delay is dependent on the crystal.

If you were to build a clock using a 60 second delay to advance the minutes, the time will only have the accuracy of the crystal.

If your crystal varies, you have no idea if the time is right.

This is why accuracy and price go hand in hand.

[ed]
Sorry, I see now.

No. If you use a 32.768 khz you can divide that down to 1hz and get a very accurate clock.
If you have a 32.768 MHZ crystal, you can do the same with no change in the clocks accuracy

It is all about the crystals PPM accuracy. The lower that number, the more accurate the clicks.

So speed doesn't matter. crystal accuracy it what matters

However, if your delay are talking about SUPER CRAZY fast delays, like on the nanosecond scale, then a crystal that does not "click" that fast will miss the time.

For instance, you want a 1uS delay, and your crystal only "clicks" every 3 uS, then you wont have an accurate delay.

But if you use a crystal that clicks 1,000,000 times a second, you will have clicks every 1uS, hence a more accurate delay.

In that aspect, faster is more accurate. But as long as the frequency "clicks" faster or right on the delay time, only the ACCURACY (PPM) of the crystal matters.
[/ed]