95 lines
4.4 KiB
Markdown
95 lines
4.4 KiB
Markdown
# N2T
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This repository contains my solutions for Nand to Tetris.
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[N2T](https://www.nand2tetris.org/) is a course that teaches how
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to build a fully functioning general-purpose computer from first
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principles. It starts with the hardware design, including its own
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instruction set for which you program an assembler. You finish the
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course with a two-step compiler that translates a high-level programming
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language called Jack into assembly code.
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Even though I have a solid understanding of microcontrollers based on my
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experience in the embedded industry, I still learned a couple of new concepts
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and improved my general knowledge of how a computer works. Going through all
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the steps to build a computer starting from first principles helps to facilitate
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a deep understanding. If you are a person that needs hands-on examples to grasp
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a concept, you will love this course as much as I do.
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In the following, I explain how to use my solutions, mainly if I want to revisit
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this class later. If you haven't done the course yet, you should not look at the
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answers, but you can try to play the game I wrote in the Jack programming
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language. It is not a game but a 1D cellular automaton simulator.
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## Project 1: Boolean Logic
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In this project, we start building the basic gates required for the computer.
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Our basic building block is a Nand gate from which we make 15 additional gates.
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We implement the gates in a simplified hardware description language (HDL). To
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test the HDL files, run `./tools/HardwareSimulator.sh` and open one of the test
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scripts located in `./projects/01`.
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## Project 2: Boolean Arithmetic
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Based on the previous projects' basic gates, we build arithmetic chips:
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a half-adder, a full adder, a 16-bit adder, and a 16-bit incrementer
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based on the simple adders. Finally, we create the ALU (arithmetic-logic
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unit), which is the heart of the CPU that we make in the later projects.
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The ALU takes two 16-bit inputs and computes an output depending on a
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couple of control-bits' status. To test the arithmetic chips, use the
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hardware simulator equally to the first project.
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## Project 3: Memory
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Till this point, all gates are stateless. To build a computer, we need
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memory. For this purpose, the course introduces a DFF (data flip-flop).
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We can create a one-bit register and build up from there to a 16k chip
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with the DFF.
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It found it rewarding to build memory from first principles, but even more
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rewarding was how easy Vim makes it to write the HDL code for these chips. The
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following picture shows how I create a 64-bit register from 8-bit registers in a
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matter of seconds.
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## Project 4: Machine Language Programming
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In project 4, we get familiar with the Hack machine language - our
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computer's assembly language. We write two basic projects: fill the
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screen when the user presses a button, and a second one that
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multiplicates two input arguments. To try the scripts, start the CPU
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emulator by executing `./tools/CPUEmulator.sh`. You can then open the
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script located in `./projects/04/fill` or `./projects/04/mult`.
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I have created a Vim syntax file for the Hack assembly language. Copy the file
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`hackasm.vim` from the vim directory into your Vim installation's syntax
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directory. You can then set the filetype to hackasm by running `:set ft=hackasm`
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from within Vim, and you should see highlighting as shown on the following
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screenshot.
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## Project 5: Computer Architecture
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In this project, we assemble all prior building blocks into the main memory,
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CPU, and finally into the full hack computer. There are test scripts similar to
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project one to three to validate that the computer works as designed. Seeing it
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all come together is incredibly rewarding. Even if you stop the course at this
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point, you have developed a great intuition of how a computer works.
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## Project 6: The Assembler
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With the computer working, we now need a way to assemble the hackasm code into
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machine instructions. The purpose of this project is to build the assembler in
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the programming language of our choice.
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My Python version has 203 lines of code and relies on Python 3.8 features. We
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can test the assembler by changing the directory to `./projects/06` and then
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running `python assembler.py pong/*.asm`. Note that my assembler can only
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translate individual asm-files and does not search a directory.
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Load the resulting hack file into the CPU emulator to verify that the
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assembler works correctly.
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