AVR, external clock

U

Umpa

Guest
Hello,

I have got AVR ATmega16.

I`m developing an application
which should receive data from
UART.
I would like to conntec external
oscilator of 11059200 Hz.
I connected it to XTAL and set
fuse "ext. clock", but processor
doesn`t work.

What to do to make my processor
working with external oscilator
and using it for UART?

Umpa.
 
What type of XTAL is it ?
What input pins are you using ?

/Anders

"Umpa" <šżćó@umpaumpalala.com> skrev i meddelandet
news:c807sf$e0b$1@atlantis.news.tpi.pl...
Hello,

I have got AVR ATmega16.

I`m developing an application
which should receive data from
UART.
I would like to conntec external
oscilator of 11059200 Hz.
I connected it to XTAL and set
fuse "ext. clock", but processor
doesn`t work.

What to do to make my processor
working with external oscilator
and using it for UART?

Umpa.
Click to expand...
 
OK
Have you connected 2 capacitors to the XTAL ?
22-33pF is mostly used, look in the datasheet.
/ Anders

"Umpa" <šżćó@umpaumpalala.com> skrev i meddelandet
news:c81uig$qlk$1@atlantis.news.tpi.pl...
What type of XTAL is it ?
It is cristal oscilator 11059200Hz

What input pins are you using ?
I am using XTAL1 and XTAL2.
Click to expand...
 
Have you connected 2 capacitors to the XTAL ?
22-33pF is mostly used, look in the datasheet.
Click to expand...
Yes. Two capacitors of 27pF connected to XTAL1
and XTAL2 and GND.

Test:

I connected 8MHz oscilator, set fuse XTAL3-8MHz.
It works.

I connected 11MHz oscilator, set fuse XTAL3-8MHz.
Doesn`t work.

I connected 11MHz oscilator, set fuse XTAL3-8MHz,
changed state of !CKOPT.
Doesn`t work

I tried a few 11MHz oscilators.

If I use oscilator slower than 8MHz there are fuses that
cover it (XTAL3-8, XTAL...)

But my oscilator is 11MHz. Atmel`s manual says that
we should change CKOPT for oscilators faster than 8MHz.
But it doesn`t help.

Umpa.
 
Is it at MEGA16 or a MEGA16L ?

"Umpa" <šżćó@umpaumpalala.com> skrev i meddelandet
news:c827js$p8n$1@nemesis.news.tpi.pl...
Have you connected 2 capacitors to the XTAL ?
22-33pF is mostly used, look in the datasheet.

Yes. Two capacitors of 27pF connected to XTAL1
and XTAL2 and GND.

Test:

I connected 8MHz oscilator, set fuse XTAL3-8MHz.
It works.

I connected 11MHz oscilator, set fuse XTAL3-8MHz.
Doesn`t work.

I connected 11MHz oscilator, set fuse XTAL3-8MHz,
changed state of !CKOPT.
Doesn`t work

I tried a few 11MHz oscilators.

If I use oscilator slower than 8MHz there are fuses that
cover it (XTAL3-8, XTAL...)

But my oscilator is 11MHz. Atmel`s manual says that
we should change CKOPT for oscilators faster than 8MHz.
But it doesn`t help.

Umpa.
Click to expand...
 
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