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A Refind Adder with Xnor Gates

A project log for LLTP - Light Logic Transistorless Processor

My attempt to create a CPU/MCU without transistors or relays

Dr. CockroachDr. Cockroach 06/18/2022 at 10:420 Comments

June 18, 2022 - I have spent way too much time away from my Light Logic projects but recently had the idea to take the current LLTP build and re-think the logic gates I have been using and try to reduce the number of gates used. The Full Adder seems to be the first area to work on and I have started on testing a Adder on Logisim that instead of using only Nand gates I will make use of a pair of Xnor gates and a 2 X 1 Mux. This will reduce the Light Logic gate count from nine to six gates for a single bit Full Adder. Over the course of a four or eight bit adder this will save me quite a few gates. Each gate requires a single opto coupler/vactrol an a few support diodes.

Logisim likes the circuit so far, so next will be a actual build and test.

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