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1 to 4 demultiplexer

A project log for The Cardboard Computer

My goal is a 4-bit cpu using discrete transistors. I am learning from scratch as I have never worked with hardware at the gate level.

Mark Nesselhaus 12/26/2016 at 09:250 Comments

December 26, 2016 - just started playing with a demultiplexer circuit on Logisim last night so here what I have so far. Top inputs are the data bus lines and left side is select inputs. The sim likes it. Each row is output bits to selected registers or whatever. Why not use AND gates? I work better using my standard Nand gate circuit.

Update 12/31/16 - I have have finished soldering the gate VLC's and about to hot glue them to the base board. I am going to wire only half of the dmux and test it that way and if all is well then wire the second half. The two gates on the left are the select gates and the top row will output to the ALU. I don't know about the second row yet.

Update 1/1/2017 - Gates are glued down and started the wiring with the positive leads. Yes, this method takes a LOT of time but it is a way for me to relax after a day of cooking.

Update 1/2/2017 - The power and ground connections are finished. Now onward with the data wiring.

Update 1/3/2017 - Ok. this is half of the dmux wired and tested good so far. That's a lot of point to point just for a 1 to 2 unit :-)

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