User's Manual

8
Atmel AVR2042
8334A-AVR-05/11
Figure 5-3. 32kHz crystal connection.
Table 5-2. 32kHz crystal connection.
ATxmega256A3 32kHz crystal
PE6 (42) TOSC2
PE7 (43) TOSC1
5.3.2 Transceiver clock (CLKM)
To make use of the transceiver clock, CLKM, an Atmel REB has to be connected to
the Atmel REB-CBB and the radio transceiver has to be set up properly on the REB.
The transceiver delivers a 1MHz clock frequency after power on. Although it is
possible to set the clock frequency up to 16MHz by writing to the transceiver register,
no frequencies above 1MHz should be used to drive the microcontroller. This is
because the signal is filtered directly at the output pin for EMI suppression to ensure
the best RF performance of the REB. To reach a system clock frequency higher than
1MHz, the Atmel XMEGA internal PLL should be used.
Table 5-3. Transceiver clock (CLKM) connection.
ATxmega256A3 Clock source
PD0 (26) CLKM 1MHz
The REB has to be modified to deliver the CLKM signal to PD0. Therefore, the
appropriate solder jumper (0Ω resistor) has to be mounted. Designators of the 0Ω
resistor are different for REB variants, and they are listed in the following table.
Table 5-4. REB specific CLKM solder jumpers.
REB name Solder jumper designator (REB)
REB230 R02
REB231 R02
REB231ED R3
REB212 R3
REB232ED R3
REB231FE2 R3
5.4 User I/O
For simple applications and debugging purposes, or just to deliver status information,
a basic user interface is provided directly on the board consisting of three LEDs and a
pushbutton.