AVR RISC Microcontroller Handbook

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Hardware Resources of AVR Microcontrollers

As noticed in the preface, the AVR microcontroller family is based on a new RISC architecture. In order to optimize code size, performance, and power consumption, the AVR architecture has incorporated a large fast-access register file and fast single-cycle instructions. The fast-access RISC register file consists of 32 general-purpose working resisters. Traditional accumulator-based architectures require large amounts of program code for data transfers between the accumulator and memory. With these 32 working registers—each of which acts as an accumulator—in AVR microcontrollers, these data transfers are eliminated.

The AVR microcontroller prefetches an instruction during the previous instruction ...