[En-Nut-Discussion] using Ethernut with an external Oscillator

Harald Kipp harald.kipp at egnite.de
Wed May 26 14:32:27 CEST 2010

Hi Dominik,

On 26.05.2010 11:26, Dominik Schröder wrote:

> I am using Ethernut in an At91SAM7xEK board based device. At the moment the
> application works fine with the typical Crystal Connection.
> In case of better reliability I want to connect an external Oscillator to
> the “XIN” pin. Regarding to that the datasheet says:


> But I don`t know, what`s the best way to change the regarding register. 

I do not have a ready-to-use solution, but the following explanation:

The CPU will start in slow clock mode. The clock is switched in
starting at

 * Enable the main oscillator. Set startup time of 6 * 8 slow
 * clock cycles and wait until oscillator is stabilized.
ldr     r1, =PMC_BASE

Thus, a little bit assembly language knowledge is required to modify this.


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