an exploration of building logic out of NAND gates.
I'm using python as kind of a poor man's HDL just because I like making my own tools. this is by no means an efficient or elegant simulator, it's just something i hacked together as i explored
see basics.py and the other files for usage. if you don't wanna spoil yourself the fun of figuring
out the gates, try not to look past basics
test.py runs all the gates and compares output with the .cmp files
pip install --user tabulate
- 1-bit Not, And, Or, Xor: not much to explain here, basic primitives implemented with NAND
- 1-bit Mux, DMux: multiplexers can be used to interleave data on a shared bus. they're basically a switch - the sel determines which input is passed through to the output (0 for a, 1 for b). the DMux does the opposite, it takes 1 input and sel decides whether it gets passed through to a or b. a Mux/DMux pair with synchronized sel can transfer data for both a and b on a single bus
- Not16, And16, Or16, Mux16, DMux16: straightforward extensions with 16-bit inputs
- Or8Way: takes 8 1-bit inputs and ORs them together
- Mux4Way16, DMux4Way16: 4-way de/multiplexer. it takes 4 inputs and has a 2-bit sel (0-3). now we're talking. this could be used in an actual computer to transfer 16 bit values between components
- Mux8Way16, DMux8Way16: 8-way de/multiplexer. it takes 8 inputs and has a 3-bit sel (0-7)
- HalfAdder: adds 2 bits together and outputs sum and carry
- FullAdder: adds 3 bits together and outputs sum and carry
- Add16: now that we have a FullAdder we can put 15 of them in cascade plus a HalfAdder for the least significant bit which doesn't start with a carry. this gives us a 16-bit adder, which we could also cascade up to higher word sizes
implements the ALU used in "From NAND to Tetris". while this is a very neat design, I plan on coming up with my own eventually
I picked up the basics from https://www.nand2tetris.org/