Modified Harvard architecture 8-bit
RISC microcontroller. Atmel's AVRs have a two-stage, single-level pipeline design.
There are the following registers:
- 32 general purpose 8-bit registers,
r31; with some alias like
pc16- or 22-bit program counter
sp8- or 16-bit stack pointer
sreg8-bit status register
r1 are fixed as usage.