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November 8, 2017 - It even counts down

A project log for The Cardboard Computer - IO is my name

My goal is a 4-bit CPU using recycled cardboard substrate and Diode Transistor Logic. This is an educational platform for me.

dr-cockroachDr. Cockroach 11/08/2017 at 23:472 Comments

While trying to solve some erratic issues with the master flip-flop I discovered that IO can count down as well as up by a value of one. By feeding in a value of 15d or 1111b I make use of 2's complement and subtract the value of one from the counter. This will work out very well for the Brainwarp language  to shift the cell pointer and cell value up or down by one. I was expecting to have to wire up additional circuits to accomplish this but find that I am already there :-)

Discussions

Eric Hertz wrote 12/10/2017 at 22:11 point

Often enough, when looking at disassembly of my c code I get confused by just that... doesn't make a whole lotta sense in most of those cases, since those cpus have both inc and dec, add and subtract... hadn't thought about how great it would be for a custom cpu! Score!

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Dr. Cockroach wrote 12/10/2017 at 23:29 point

Good evening Eric. Yeah I seem to learn new things with this project even if I was not looking for it yet :-) It's neat to watch IO step up or down with the flip of a few data input switches :-)

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