15 GPR - General Purpose Registers

The AVR32SD20/28/32 devices provide four General Purpose registers (GPR[3:0]). These registers can be used for storing any information, and they are particularly useful for storing global variables and interrupt flags. The GPRn are reset to 0x00 only by either a Brown-out Reset (BOR) or a Power-on Reset (POR). These registers, which reside in the address range 0x1C-0x1F, are directly bit-accessible using the SBI, CBI, SBIS, and SBIC instructions.