Michael
unread,Nov 18, 2011, 5:59:23 PM11/18/11Sign in to reply to author
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to linuxstamp
The embedded SAM-BA ROM code on the 9x25 chip switches to the internal
32 KHz RC oscillator (not external crystal, but internal RC) to do an
approximate measurement of the actual frequency of the external
(presumed) 12 MHz oscillator (crystal). This does not mean you have
to have a 32 KHz crystal hooked up to the chip. If you do, you can
enable it later for more accurate watchdog and RTC behavior. I
presume the 9g20 does the same trick. This is actually very smart,
and you can run the chip without any external crystal at all if you
are not too concerned about absolute clock frequency (subsystems like
USB or Ethernet might get torqued-up, however, if you were very far
from 12 MHz).
- Michael