Atmel AVR XMEGA-A3BU, Application Note

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Atmel AVR1923
9
8394B-AVR-02/12
5 Peripherals
5.1 Serial flash
The Atmel AVR XMEGA-A3BU Xplained has an external Atmel AVR AT45DB642D
DataFlash device mounted. A footprint is also available for adding an industrial
standard serial flash like the AT25 series from Atmel. Compatible serial flash devices
for both footprints are listed in
Table 5-2 and the connection to the MCU is shown in
Table 5-1 .
The footprints share the same SPI lines including the chip select, and therefore it is
not possible to mount devices on both footprints at the same time.
Table 5-1. Serial flash connection.
Pin on XMEGA Serial flash
PD1 SCK
PD3 MOSI
PD2 MISO
PF4 SS
Table 5-2. Compatible devices for the footprints.
Atmel AVR AT45DB Atmel AVR AT25DF
AT45DB64D2-CNU (mounted) AT25DF641A-SH
AT45DB321D-MWU AT25DF321A-SH
AT45DB161D-SS AT25DF161-SH
AT45DB081D-SS AT25DF081-SSH
AT45DB041D-SS AT25DF021-SSH
AT45DB021D-SS
AT45DB011D-SS
5.2 Atmel AVR QTouch button
The XMEGA-A3BU Xplained kit has one Atmel QTouch button and the connection to
the Atmel AVR XMEGA is shown in
Table 5-3 . The QTouch sensor, a copper fill, is
located on the second layer of the board (same as GND layer). The sensor is
shielded by the third layer (VCC layer) and therefore the sensor is not affected by any
touches from the back side of the board.
Table 5-3. QTouch button connection.
Pin on XMEGA QButton
PF6 SNS
PF7 SNSK
5.3 Battery backup system
The battery backup system backs up the RTC of the XMEGA. It consists of a coin cell
battery, a battery holder and a jumper that can be used to disconnect the battery from
the XMEGA. A manganese dioxide lithium battery (CR1220) from Panasonic with a
nominal voltage of 3V and nominal capacity of 35mAh is used in this design. In order