User's Manual

6
Atmel AVR2042
8334A-AVR-05/11
5 Functional description
The Atmel REB-CBB carries a high-performance Atmel AVR XMEGA microcontroller,
which connects to the radio extender board and various peripheral units (see Figure
5-1). It is powered by two AAA batteries or optionally by applying an external voltage
source.
Figure 5-1. REB-CBB block diagram.
5.1 Power supply
The board is powered by two AAA batteries. The power switch, SW1, disconnects
batteries from the entire board. External power is not routed through the power
switch.
For debugging and test purposes, power can also be supplied at pin header PWR.
NOTE There is no protection against over voltage.
Take care when applying power from an external source. Refer to Section 7.1 for
allowable input voltage range. Exceeding these limits may destroy the board. In
addition, avoid applying reverse currents into batteries by switching SW1 to the off
position, or by removing the batteries when using external power
Figure 5-2. Power supply of the REB-CBB.
5.2 Microcontroller
The Atmel XMEGA A3 is a family of low-power, high–performance, and peripheral-
rich CMOS 8/16-bit microcontrollers based on the AVR enhanced RISC architecture.
By executing powerful instructions in a single clock cycle, the Atmel XMEGA A3
achieves throughputs of up to 1 million instructions per second (MIPS) per MHz,
allowing the system designer to optimize power consumption versus processing