Pages: [1]   Go Down
Author Topic: Quartz Oscilator on Atmel's chips  (Read 658 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Jr. Member
**
Karma: 0
Posts: 88
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I've noticed that while the  atmega 328 requires a 16MHz oscillator (if i am correct), some smaller atmega chips like the attiny85 doesn't require one.
Why is that?
How can i know whether an atmega chip requires one or not?

Any help is appreciated smiley
« Last Edit: December 12, 2012, 04:10:36 pm by Voidugu » Logged

Global Moderator
Dallas
Offline Offline
Shannon Member
*****
Karma: 207
Posts: 12912
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

I've noticed that while the  atmega 328 requires a 16MHz oscillator (if i am correct),

You are not.

Quote
How can i know whether an atmega chip requires one or not?

Datasheet.  This is the datasheet for the ATmega328P... http://www.atmel.com/Images/doc8161.pdf

The section of interest is...
8. System Clock and Clock Options
8.2 Clock Sources through 8.8 External Clock
Logged

Left Coast, CA (USA)
Offline Offline
Brattain Member
*****
Karma: 361
Posts: 17294
Measurement changes behavior
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Also you might want to know that there is a difference between a 'crystal resonator' and a 'crystal oscillator'. Both can be used as to control the clock speed of a 328p chip as well as several other internal or external means and methods. The Arduino board uses a 16 Mhz crystal resonator to control the chip's clock speed.

Lefty
Logged

Offline Offline
Edison Member
*
Karma: 116
Posts: 2205
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
there is a difference between a 'crystal resonator' and a 'crystal oscillator'.

Absolutely.

One exists and the other doesn't.
One is real and the other isn't.
Logged

Global Moderator
Dallas
Offline Offline
Shannon Member
*****
Karma: 207
Posts: 12912
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset


http://www.vanlong.com/products/crystal.htm
...sells Crystal Resonators

http://www.vectron.com/products/xo/xo_index.htm
...sells Crystal Oscillators

Which one doesn't exist?
Logged

vermont
Offline Offline
Sr. Member
****
Karma: 8
Posts: 313
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

crystal oscillators contain a quartz crystal resonator inside along with additional internal solid state devices and cost several times more. oscillators have 4 pins, need a power supply, and put out a clock signal while crystals have 2 pin and do not.
Logged

Valencia, Spain
Offline Offline
Faraday Member
**
Karma: 146
Posts: 5507
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I've noticed that while the  atmega 328 requires a 16MHz oscillator (if i am correct), some smaller atmega chips like the attiny85 doesn't require one.
Why is that?

a) The 328 doesn't require one
b) You can choose between several clock sources. One of them is an internal oscillator.

OTOH the internal oscillators aren't very accurate, they vary with temperature and voltage. For accurate timing you need an external crystal.
Logged

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

Pages: [1]   Go Up
Jump to: