I have recently written and published a book on designing and building a 16-bit CPU. It’s called: Mission Impossible - Design and Build a CPU from Scratch. The CPU is built on the Alchitry Au FPGA board. The book is available in paperback and eBook formats at Amazon, iBooks, or Lulu Publishing.
This book is intended for electronics and computer hobbyists with no previous experience with FPGAs or with designing their own CPU. The CPU is fully functional, but simple and easy to understand. It is programmed using assembly language, without any high level language, so programs are kept fairly basic. This book should help the reader understand how CPUs work, how to design a simple one, provide an introduction to FPGAs, and an introduction to assembly language programming.
Because you can’t do much with just a CPU, my design includes ROM, RAM, serial communication, digital I/O, a timed interrupt, and even a simple A/D converter. So it is really a primitive microcontroller. The inspiration for the design is a simple 8 bit CPU originally presented by Justin Rajewski, Alchitry’s founder. I have expanded his design and added many additional features, but as CPUs go, this one is still pretty basic.
All of the code for both the FPGA hardware and all the CPU code is available on GitHub.
