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

[Harald Kipp]

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
nut/arch/arm/init/crtat91sam7sex.S
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.


Harald