Connect the external memory chosen as
required in table “DDR I/O Calibration and DDR Voltage Reference” in the Electrical
Characteristics chapter of the SAM9X7 Series data
sheet.
The DDR_CAL pin must be connected to
ground via a 20 kΩ high precision calibration resistor, both for DDR2 and DDR3L SDRAM
devices.
Connect the DDR_VREF pin to a filtered high precision voltage divider which outputs
VDDIOM/2.
The online versions of the documents are provided as a courtesy. Verify all content and data in the device’s PDF documentation found on the device product page.
