Crystal Issue in Atmel AT89S8253?

[g_shyam1682]

Hello friends,

I am using Atmel AT89S8253.
Currently I am using crystal 20 MHz with 27 pf ceramic capacitor, I am facing following problems

-- It dows processor speed upto 1/3. sometimes result it hang processor
-- Sometimes crystal is defected.

I am looking for option for same.

so guys do you have any suggestion???

Suggestion is highly appreciated
Thanks in advance

 

[FvM]

According to the datasheet, you should not add above 10 pF external capacitance at XTAL1 and XTAL2 each.
It's known that the oscillator may fail otherwise.

 

[g_shyam1682]

thnaks for your response

According to your reply I have tried 10 pf at both leg XTAL1 and XTAL2
But it decrease processor speed 1/4th time.
If I remove capacitor from XTAL2, I get normal processor speed.

I want to use capacitor on both lag due to sometime it fails my crystal.

thanks again

 

[FvM]

I'm not using the particular chip, so I can't tell about special issues. You should generally assume, that the datasheet is correct.
But it seems to me, that something is very wrong, either with your crystal or with your circuit assembly. It's almost impossible
to identify the problem from a distance.

 

[IanP]

The AT89S8253 is known to have certain issues as far as the crystal connections are concerned, so you are not the only one who has to deal with that ..
**broken link removed**

In some cases, external capacitors C1 and C2 may NOT be required due to the onchip capacitance of the XTAL1 and XTAL2 inputs (approximately 10 pF each) ..

If the problem persists, try another AT89S8253 from different batch or use an external TCXO ..

Rgds,
IanP