The AVR core combines a rich instruction set with 32 general-purpose working registers. All the 32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be accessed in one single instruction executed in one clock cycle. The resulting architecture is more code efficient while achieving throughputs up to ten times faster than conventional CISC microcontrollers.
The AT90S8515 provides the following features: 8K bytes of In-System Programmable Flash, 512 bytes EEPROM, 512 bytes SRAM, 32 general-purpose I/O lines, 32 general purpose working registers, flexible timer/counters with compare modes, internal and external interrupts, a programmable serial UART, programmable Watchdog Timer with internal oscillator, an SPI serial port and two software-selectable power-saving modes. The Idle Mode stops the CPU while allowing the SRAM, timer/counters, SPI port and interrupt system to continue functioning. The Power-down mode saves the register contents but freezes the oscillator, disabling all other chip functions until the next external interrupt or hardware reset.

FEATUREs
• Utilizes the AVR® RISC Architecture
• AVR – High-performance and Low-power RISC Architecture
   – 118 Powerful Instructions – Most Single Clock Cycle Execution
   – 32 x 8 General-purpose Working Registers
   – Up to 8 MIPS Throughput at 8 MHz
• Data and Nonvolatile Program Memory
   – 8K Bytes of In-System Programmable Flash Endurance: 1,000 Write/Erase Cycles
   – 512 Bytes of SRAM
   – 512 Bytes of In-System Programmable EEPROM Endurance: 100,000 Write/Erase Cycles
   – Programming Lock for Flash Program and EEPROM Data Security
• Peripheral Features
   – One 8-bit Timer/Counter with Separate Prescaler
   – One 16-bit Timer/Counter with Separate Prescaler Compare, Capture Modes and Dual 8-, 9-, or 10-bit PWM
   – On-chip Analog Comparator
   – Programmable Watchdog Timer with On-chip Oscillator
   – Programmable Serial UART
   – Master/Slave SPI Serial Interface
• Special Microcontroller Features
   – Low-power Idle and Power-down Modes
   – External and Internal Interrupt Sources
• Specifications
   – Low-power, High-speed CMOS Process Technology
   – Fully Static Operation
• Power Consumption at 4 MHz, 3V, 25°C
   – Active: 3.0 mA
   – Idle Mode: 1.0 mA
   – Power-down Mode: <1 µA
• I/O and Packages
   – 32 Programmable I/O Lines
   – 40-lead PDIP, 44-lead PLCC and TQFP
• Operating Voltages
   – 2.7 - 6.0V for AT90S8515-4
   – 4.0 - 6.0V for AT90S8515-8
• Speed Grades
   – 0 - 4 MHz for AT90S8515-4
   – 0 - 8 MHz for AT90S8515-8