The SAM4E Xplained Pro kit contains two crystals that can be used
as clock sources for the SAM4E device. Each crystal has a cut-strap next to it that can be
used to measure the oscillator safety factor. This is done by cutting the strap and adding
a resistor across the strap. More information about oscillator allowance and safety factor
can be found in the Atmel application note AVR4100: Selecting and testing 32kHz crystal oscillators for Atmel AVR
microcontrollers.
Table 1. External 32.768kHz
Crystal| Pin on SAM4E |
Function |
|---|
| PA7 |
XIN32 |
| PA8 |
XOUT32 |
Table 2. External 12MHz
Crystal| Pin on SAM4E |
Function |
|---|
| PB9 |
XIN |
| PB8 |
XOUT |
Important: Load capacitor
calculation, selection and verification was done wrong in the design of the SAM4E Xplained
Pro evaluation kit, see the errata section for more
information.