Atmel Xplained Pro Evaluation Kit ATSAMD20-XPRO ATSAMD20-XPRO Data Sheet
Product codes
ATSAMD20-XPRO
612
Atmel | SMART SAM D20 [DATASHEET]
Atmel-42129K–SAM-D20_datasheet–06/2014
resistors can be used, e.g. the pins can be configured in pull-up or pull-down mode eliminating the need for external
components, for more information see
components, for more information see
for details. There are no obvious benefit in choosing external
vs. internal pull resistors.
34.6
Clocks and Crystal Oscillators
The SAM D20 can be run from internal or external clock sources, or a mix of internal and external sources. An example
of usage will be to use the internal 8MHz oscillator as source for the system clock, and an external 32.768kHz watch
crystal as clock source for the Real-Time counter (RTC).
of usage will be to use the internal 8MHz oscillator as source for the system clock, and an external 32.768kHz watch
crystal as clock source for the Real-Time counter (RTC).
34.6.1 External Clock Source
Figure 34-5. External Clock Source Example Schematic
34.6.2 Crystal Oscillator
Figure 34-6. Crystal Oscillator Example Schematic
The crystal should be located as close to the device as possible. Long signal lines may cause too high load to operate
the crystal, and cause crosstalk to other parts of the system.
the crystal, and cause crosstalk to other parts of the system.
Table 34-5. Crystal Oscillator Checklist
Notes: 1.
These values are given only as typical example.
Table 34-4. External Clock Source Connections
Signal Name
Recommended Pin Connection
Description
XIN
XIN is used as input for an external clock signal
Input for inverting oscillator pin
XOUT/GPIO
Can be left unconnected or used as normal GPIO
XOUT/GPIO
XIN
NC/GPIO
External
Clock
Signal Name
Recommended Pin Connection
Description
XIN
Load capacitor 15pF
External crystal between 0.4 to 30MHz
XOUT
Load capacitor 15pF
XOUT
XIN
15pF
15pF