63 lines
3.1 KiB
Plaintext
63 lines
3.1 KiB
Plaintext
// 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/02/ALU.hdl
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/**
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* The ALU (Arithmetic Logic Unit).
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* Computes one of the following functions:
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* x+y, x-y, y-x, 0, 1, -1, x, y, -x, -y, !x, !y,
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* x+1, y+1, x-1, y-1, x&y, x|y on two 16-bit inputs,
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* according to 6 input bits denoted notZX,nx,notZY,ny,f,no.
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* In addition, the ALU computes two 1-bit outputs:
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* if the ALU output == 0, zr is set to 1; otherwise zr is set to 0;
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* if the ALU output < 0, ng is set to 1; otherwise ng is set to 0.
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*/
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// Implementation: the ALU logic manipulates the x and y inputs
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// and operates on the resulting values, as follows:
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// if (notZX == 1) set x = 0 // 16-bit constant
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// if (nx == 1) set x = !x // bitwise not
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// if (notZY == 1) set y = 0 // 16-bit constant
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// if (ny == 1) set y = !y // bitwise not
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// if (f == 1) set out = x + y // integer 2's complement addition
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// if (f == 0) set out = x & y // bitwise and
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// if (no == 1) set out = !out // bitwise not
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// if (out == 0) set zr = 1
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// if (out < 0) set ng = 1
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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 (if 1) or x & y (if 0)
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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, // 1 if (out == 0), 0 otherwise
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ng; // 1 if (out < 0), 0 otherwise
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PARTS:
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// Put you code here:
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Not(in=zx,out=notZX);
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Not(in=zy,out=notZY);
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And16(a[0]=notZX,a[1]=notZX,a[2]=notZX,a[3]=notZX,a[4]=notZX,a[5]=notZX,a[6]=notZX,a[7]=notZX,a[8]=notZX,a[9]=notZX,a[10]=notZX,a[11]=notZX,a[12]=notZX,a[13]=notZX,a[14]=notZX,a[15]=notZX,b=x,out=ZX);
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And16(a[0]=notZY,a[1]=notZY,a[2]=notZY,a[3]=notZY,a[4]=notZY,a[5]=notZY,a[6]=notZY,a[7]=notZY,a[8]=notZY,a[9]=notZY,a[10]=notZY,a[11]=notZY,a[12]=notZY,a[13]=notZY,a[14]=notZY,a[15]=notZY,b=y,out=ZY);
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Xor16(a[0]=nx,a[1]=nx,a[2]=nx,a[3]=nx,a[4]=nx,a[5]=nx,a[6]=nx,a[7]=nx,a[8]=nx,a[9]=nx,a[10]=nx,a[11]=nx,a[12]=nx,a[13]=nx,a[14]=nx,a[15]=nx,b=ZX,out=NX);
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Xor16(a[0]=ny,a[1]=ny,a[2]=ny,a[3]=ny,a[4]=ny,a[5]=ny,a[6]=ny,a[7]=ny,a[8]=ny,a[9]=ny,a[10]=ny,a[11]=ny,a[12]=ny,a[13]=ny,a[14]=ny,a[15]=ny,b=ZY,out=NY);
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Add16(a=NX,b=NY,out=sumout);
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And16(a=NX,b=NY,out=andout);
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Not(in=f,out=notF);
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And16(a[0]=f,a[1]=f,a[2]=f,a[3]=f,a[4]=f,a[5]=f,a[6]=f,a[7]=f,a[8]=f,a[9]=f,a[10]=f,a[11]=f,a[12]=f,a[13]=f,a[14]=f,a[15]=f,b=sumout,out=out1);
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And16(a[0]=notF,a[1]=notF,a[2]=notF,a[3]=notF,a[4]=notF,a[5]=notF,a[6]=notF,a[7]=notF,a[8]=notF,a[9]=notF,a[10]=notF,a[11]=notF,a[12]=notF,a[13]=notF,a[14]=notF,a[15]=notF,b=andout,out=out2);
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Xor16(a=out1,b=out2,out=out3);
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Xor16(a[0]=no,a[1]=no,a[2]=no,a[3]=no,a[4]=no,a[5]=no,a[6]=no,a[7]=no,a[8]=no,a[9]=no,a[10]=no,a[11]=no,a[12]=no,a[13]=no,a[14]=no,a[15]=no,b=out3,out=output);
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And16(a=output,b=output,out=out);
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Not16(in=output,out=notOut);
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Add16Way(in=notOut,out=zr);
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CheckPin16(in=output,out=ng);
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} |