ATMEL Atmel AVR micro controller AT90PWM1 handbook

is a high-performance, low-power AVR ® 8-bit microcontroller. It uses an advanced RISC architecture, 131 powerful instructions, most of which can be executed in a single clock cycle. 32 8-bit general purpose working registers, fully static operation, 1MIPS throughput per MHz, on-chip 2-cycle multiplier.