6.4.5 Register File
The register file consists of 32 8-bit general purpose working registers used by the CPU. The register file is located in a separate address space from the data memory.
All CPU instructions that operate on working registers have direct and single-cycle access
to the register file. Some limitations apply to which working registers can be accessed by
an instruction, like the constant arithmetic and logic instructions SBCI
,
SUBI
, CPI
, ANDI
, ORI
and LDI
. These instructions apply to the second half of the working
registers in the register file, R16 to R31. See the AVR Instruction Set Manual for
further details.