Crystal Oscillator

Created Tue, 08 May 2012 12:36:24 +0000 by rpbehera

rpbehera

Tue, 08 May 2012 12:36:24 +0000

The crystal oscillator frequency used on chipKIT32 board is 8MHZ, but how can it work for 80MHZ as per the datasheet of the board. Pl. explain.

MCHPSupport

Tue, 08 May 2012 15:22:58 +0000

There is a PLL (Phase Locked Loop) within the MCU which gives the ability to multiply the frequency of the external crystal. More about this feature can be found in the Oscillator section of the FRM which can be found here. [url]http://ww1.microchip.com/downloads/en/DeviceDoc/61112G.pdf[/url]

If you are programming with MPIDE, I believe the configuration bits are already set to enable 80MHz operation. This can be seen in Mark's Post: ([url]http://www.chipkit.org/forum/viewtopic.php?f=6&t=35&p=154&hilit=pll#p154[/url])

If using MPLAB and programming the chipKIT via a PICKit 3 (or other programmer), then the following configuration bits will set the device up for 80MHz operation.

A great way to verify the frequency of your oscillator is to set up a timer for a one second interrupt and toggling a pin. There is an example of this here for use with MPLAB. [url]http://www.chipkit.org/forum/viewtopic.php?f=17&t=790[/url]

Regards, Josh

michael83

Thu, 18 Oct 2012 01:58:58 +0000

The PLL helps the oscillator to amplify the capabilities of the oscillator that's why the 8MHZ oscillator becomes 80 MHZ and also with the help of the program of the circuit.