Open8: Open Source 8-bit Microcontroller Architecture

Architecture Goals

• Low power consumption and cost
• Easy to learn and develop
• Flexible I/O configuration
• Support for modern toolchains

Core Processor

• 8-bit RISC instruction set, most instructions execute in a single cycle
• 16-bit Program Counter (PC), supporting 64KB program space
• 32 general-purpose 8-bit registers (R0–R31)
• 2-stage pipeline (fetch, execute)

Memory Architecture

• Separate program memory (Flash) and data memory (SRAM)
• 2KB–8KB SRAM (depending on model)
• 16KB–64KB Flash
• 256B EEPROM (optional)

I/O and Peripherals

• 32 programmable I/O pins
• Two 8-bit timers/counters (with PWM)
• One 16-bit timer/counter
• SPI, I2C, and UART interfaces
• 8-channel 10-bit ADC
• External interrupt support

Instruction Set Features

• AVR-inspired, compact and easy to decode
• Bit manipulation, shift, arithmetic, and logic operations
• Direct, indirect, and immediate addressing modes
• Multiple jump and branch instructions

Power Management

• Multiple power-saving modes (Idle, Power-down, Standby)
• 1.8V–5.5V operating voltage

Development Tools

• GCC/LLVM support
• Open-source simulator
• Standard JTAG/SWD debug interface