Sunday, December 18, 2011

It's alive!

After implementing an 8-bit full adder, I decided to turn it into an 8-bit ALU.  The ALU supports addition, subtraction, NOT, OR, and AND.  It's considerably more complicated than the full-adder, but at the same time I'm happy with the degree of reuse I was able to achieve.  The addition of support for AND, for example, required only the addition of a 2-1 mux per bit (2 74HCT157s for the whole ALU).

I've wired up two bits so far, and have started testing to ensure that the basics are sound before I turn it into even more of a rats nest.  This turns out to have been a wise choice, as I made a few mistakes with the control bits -- mistakes which are much easier to correct with two bits than four.

I'll post schematics and diagrams when I get all eight bits done.

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