To reduce the components amount I don't want to put the 32.768 kHz oscillator on my own Due. Can I leave the corresponding XTAL inputs unconnected?

What is the main target of the slow clock? What I can not do with the high clock but can do with the slow one? Will I face to any issues if I don't use the low freq. oscillator?

2 Answers 2


The slow clockr is primarily used for the real time clock (RTC) module inside the SAM3X chip. It can also be routed to other places when you want a low speed clock source, but the only places it is actually required are the RTC and the watchdog.

The slow clock can be generated from an internal RC oscillator instead of requiring an external crystal, but the accuracy and stability of the RC oscillator is many orders of magnitude worse than a crystal. Trying to use that for the RTC module will result in the clock drifting over time. The watchdog won't really care if the clock isn't perfectly accurate.

  • So I can safely go without slow clock oscillator and my Due will work. What about the xtal pins. Can I leave them unconnected? I didn't find any info about that.
    – Tigran
    Sep 24, 2015 at 7:40

Atmel datasheet says:

If the user does not need the crystal oscillator, the XIN32 and XOUT32 pins can be left unconnected

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