90 lines
2.5 KiB
Plaintext
Executable File
90 lines
2.5 KiB
Plaintext
Executable File
// This file is part of www.nand2tetris.org
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// and the book "The Elements of Computing Systems"
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// by Nisan and Schocken, MIT Press.
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// File name: projects/2/ALU.hdl
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/**
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* ALU (Arithmetic Logic Unit):
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* Computes out = one of the following functions:
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* 0, 1, -1,
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* x, y, !x, !y, -x, -y,
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* x + 1, y + 1, x - 1, y - 1,
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* x + y, x - y, y - x,
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* x & y, x | y
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* on the 16-bit inputs x, y,
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* according to the input bits zx, nx, zy, ny, f, no.
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* In addition, computes the two output bits:
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* if (out == 0) zr = 1, else zr = 0
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* if (out < 0) ng = 1, else ng = 0
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*/
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// Implementation: Manipulates the x and y inputs
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// and operates on the resulting values, as follows:
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// if (zxxx // 16-bit constant
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// if (nx == 1) sets x = !x // bitwise not
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// if (zy == 1) sets y = 0 // 16-bit constant
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// if (ny == 1) sets y = !y // bitwise not
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// if (f == 1) sets out = x + y // integer 2's complement addition
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// if (f == 0) sets out = x & y // bitwise and
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// if (no == 1) sets out = !out // bitwise not
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CHIP ALU {
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IN
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x[16], y[16], // 16-bit inputs
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zx, // zero the x input?
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nx, // negate the x input?
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zy, // zero the y input?
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ny, // negate the y input?
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f, // compute (out = x + y) or (out = x & y)?
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no; // negate the out output?
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OUT
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out[16], // 16-bit output
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zr, // if (out == 0) equals 1, else 0
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ng; // if (out < 0) equals 1, else 0
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PARTS:
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// zx
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Mux16(a=x, b[0..15]=false , sel=zx, out=zeroedX);
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// nz
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Not16(in=zeroedX, out=notX);
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Mux16(a=zeroedX,b=notX,sel=nx, out=processedX);
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//zy
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Mux16(a=y, b[0..15]=false , sel=zy, out=zeroedY);
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//ny
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Not16(in=zeroedY, out=notY);
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Mux16(a=zeroedY,b=notY,sel=ny, out=processedY);
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// f
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And16(a=processedX , b=processedY , out=andXY);
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Add16(a=processedX , b=processedY , out=addXY);
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Mux16(a=andXY, b=addXY,sel=f, out= fOut );
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// no
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Not16(in=fOut, out=notF);
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Mux16(a=fOut, b=notF, sel=no,
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// variable wire
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out[0..7]=finalResultp1,
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out[8..15]=finalResultp2,
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// out
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out=out,
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out[15]=ng
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);
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//zr
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Or8Way(in=finalResultp1 , out=zr8wayoutp1);
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Or8Way(in=finalResultp2 , out=zr8wayoutp2);
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Or(a=zr8wayoutp1, b= zr8wayoutp2, out=zrOut);
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Not(in= zrOut, out= zr);
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//ng
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// output from Mux16 in no
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//// Replace this comment with your code.
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} |