Many years ago I completed the challenge to fit a CPU into the smallest available CPLD on the market - the MCPU. Ever since then I have been pondering about a new challenge in minimalism in CPU-Design. I had completed a TTL-based CPU even before the MCPU. Clearly, the only direction left is to go fully discrete and build a minimal CPU out of discrete transistors.
To make things interesting and add a modern twist, I decided to investigate a logic family that uses light emitting diodes (LEDs) as an active element. LTL is a logic family from a past that never happened. It combines 1950s transistor logic with low current green InGaN LEDs that were invented in the 1990s.
I already completed the design up to a prototype of a sub-system (see header image) and will use this project to document the steps I have taken to get there.