HALB-CPU

This is a design document for simple, yet reasonably functional CPU that is possible to build from scratch in home. By "from scratch" I mean using nothing more than discrete transistors, diodes, resistors and whatever needed for connecting them. There might be some exceptions, such as clock generation or I/O, but the core should follow these principles.

TL;DR

ROM and RAM are separate 16-bit address spaces with 8-bit data cells; RISC-style ISA with 4 registers, two of which can act as pointer; all in TTL logic; opcodes take 1-2 cycles.

Table of contents

• General issues
• Transistor technology (DTL vs TTL)
• Opcodes
• ALU design
• Clock generation
• Loading program