8.12.2 Extended I/O Registers

The I/O memory space ranging from 0x0040 to 0x103F can only be accessed by the LD/LDS/LDD or ST/STS/STD instructions, transferring data between the 32 general purpose working registers (R0-R31) and the I/O memory space.

For further details, refer to the Peripheral Address Map table and the Instruction Set Summary section.