Atmel Evaluation Kit AT91SAM9M10-G45-EK AT91SAM9M10-G45-EK Data Sheet

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SAM9M10 [DATASHEET]

6355F–ATARM–12-Mar-13

To switch from internal RC oscillator to the 32768 Hz crystal, the programmer must execute the following
sequence:

• Switch the master clock to a source different from slow clock (PLLA or PLLB or Main Oscillator) through the 

Power management Controller.

• Enable the 32768 Hz oscillator by setting the bit OSCEN to 1.

• Wait 

32768 Hz Startup Time for clock stabilization (software loop)

• Switch from internal RC to 32768Hz by setting the bit OSCSEL to 1.

• Wait 5 slow clock cycles for internal resynchronization

• Disable the RC oscillator by setting the bit RCEN to 0.

The following step must be added to bypass the 32768Hz Oscillator.

• An external clock must be connected on XIN32.

• Enable the bypass path OSC32BYP bit set to 1.

• Disable the 32768 Hz oscillator by setting the bit OSC32EN to 0.

The same procedure must be followed to switch from 32768Hz crystal to the internal RC oscillator. 

• Switch the master clock to a source different from slow clock (PLLA or PLLB or Main Oscillator) 

• Enable the internal RC oscillator by setting the bit RCEN to 1.

• Wait 

internal RC Startup Time for clock stabilization (software loop)

• Switch from 32768Hz oscillator to internal RC by setting the bit OSCSEL to 0

• Wait 5 slow clock cycles for internal resynchronization

• Disable the 32768Hz oscillator by setting the bit OSC32EN to 0