DAC null voltage for (DAC1,0) ?

hello,
i'm running the following code on a due
....
void loop() {

analogWriteResolution(12);

analogWrite (DAC1,0);
delay (10000);
analogWrite (DAC1,100) ;
delay (5000);
analogWrite (DAC1,0);
delay (5000);
analogWrite (DAC1, 200) ;
delay (5000);
analogWrite (DAC1,0);

etc.....

i can see the voltage steps on the scope but for analogWrite
(DAC1,0) i have 537mV an so on
DAC1,100 => 591
DAC1,200 => 645
DAC1,300 => 699
DAC1,400 => 753

i was expecting DAC1,0 to give me 0mV

any thought on what i'm doing wrong ?

cheers
Francois

PS: same problem on DAC0

The dac got a voltage offset of 1/6 of 3.3v. The max voltage is 5/6 of 3.3v.

i had same issue before. please check this.
http://forum.arduino.cc/index.php?topic=173747

thanks for you help guys,

to sum up

from wibauxl
But on page 1059 of SAM3S datasheet, it is said that the voltage range of the DAC is from (1/6) x VADVREF to (5/6) x VADVREF.
So I suspect, the same applies to SAM3U, and range is 1/6 x 3.3V = 0.55V to 5/6 x 3.3V = 2.75V, which is verified by your measures.