The Not Quite Simple As Possible Computer

The NQSAP is a breadboard TTL computer that follows the Ben Eater 8-bit computer (SAP-1) design with some enhancements and extensions.

Highlights of the design are:

• 6502-inspired instruction set that provides equivalents to most of the instructions and addressing modes
• 8-bit addressing extends the size of memory and number of opcodes
• 74LS181 ALU instead of adder provides arithmetic and logic operations including add, subtract, AND, OR, and XOR
• Arduino-based loader/debugger to load programs and run interactive diagnostics
• 3-to-8 Decoders for register selection simplifies wiring and reduces the number of microcode bits needed while also protecting against inadvertent bus collisions
• 8-bit Stack Pointer for storage and subroutines

This repo contains:

• NQSAP documentation
• Arduino-based Microcode programmer
• Arduino Nano-based System Loader / Debugger