I can't locate (because there is no circuit designations: Y1 and Y2 on the board) the above-mentioned crystals on my newly-purchased Arduino DUE Board.
However, uploaded sketches work!
Am I correct to say that the crystals are not placed by the manufacturer, and the MCU is using the internal RC-based oscillators?
The default oscillators used (in the arduino environment) are the internal RC oscillators (12 MHz then the PLL to achieve 84 MHz and the slow clock 32768 Hz).
Beware: if your board doesn't have the external crystal whereas you try to initialize the board with it, the board will become a brick.
DUE with external XTAL.doc (185 KB)
Should be as shown in this picture. I see photos around of Dues with no 32kHz crystal, but they all seem to have the 12MHz crystal. The code (in system_sam3xa.c) claims to switch to the external crystal...
/* Switch to 3-20MHz Xtal oscillator */
PMC->CKGR_MOR = CKGR_MOR_KEY_PASSWD | SYS_BOARD_OSCOUNT | CKGR_MOR_MOSCRCEN | CKGR_MOR_MOSCXTEN | CKGR_MOR_MOSCSEL;
Beware: if your board doesn't have the external crystal whereas you try to initialize the board with it, the board will become a brick.
Nah. That's true of AVRs, where the clock selection is done via fuse. On Due, the chip always starts on an internal oscillator, and uses SW to switch to other modes.
Following the Pictorial View of Post#2, I have been able to locate 12 MHz crystal on my Arduino DUE Board. The 32.768 KHz crystal is really missing; there are two empty solder pads!