 Some small models also map the program ROM into the data address space, but larger models do not.The AVRs have 32 single-byte registers and are classified as 8-bit RISC devices.In the tinyAVR and megaAVR variants of the AVR architecture, the working registers are mapped in as the first 32 memory addresses (000016–001F16), followed by 64 I/O registers (002016–005F16).