hw4.md

第五週

ALU

// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/02/ALU.hdl
/**

The ALU (Arithmetic Logic Unit).
Computes one of the following functions:
x+y, x-y, y-x, 0, 1, -1, x, y, -x, -y, !x, !y,
x+1, y+1, x-1, y-1, x&y, x|y on two 16-bit inputs,
according to 6 input bits denoted zx,nx,zy,ny,f,no.
In addition, the ALU computes two 1-bit outputs:
if the ALU output == 0, zr is set to 1; otherwise zr is set to 0;
if the ALU output < 0, ng is set to 1; otherwise ng is set to 0.
*/

// Implementation: the ALU logic manipulates the x and y inputs
// and operates on the resulting values, as follows:
// if (zx == 1) set x = 0        // 16-bit constant
// if (nx == 1) set x = !x       // bitwise not
// if (zy == 1) set y = 0        // 16-bit constant
// if (ny == 1) set y = !y       // bitwise not
// if (f == 1)  set out = x + y  // integer 2's complement addition
// if (f == 0)  set out = x & y  // bitwise and
// if (no == 1) set out = !out   // bitwise not
// if (out == 0) set zr = 1
// if (out < 0) set ng = 1
CHIP ALU {
IN

x[16], y[16],  // 16-bit inputs

zx, // zero the x input?
nx, // negate the x input?
zy, // zero the y input?
ny, // negate the y input?
f,  // compute out = x + y (if 1) or x & y (if 0)
no; // negate the out output?
OUT 
    out[16], // 16-bit output
    zr, // 1 if (out == 0), 0 otherwise
    ng; // 1 if (out < 0),  0 otherwise

PARTS:

// Put you code here:
//ALU
//level1(zx,zy)
Mux16(a=x,b=false,sel=zx,out=x1);
Mux16(a=y,b=false,sel=zy,out=y1);

//level2(Not16,nx,ny)
Not16(in=x1,out=nx1);
Not16(in=y1,out=ny1);
Mux16(a=x1,b=nx1,sel=nx,out=x2);
Mux16(a=y1,b=ny1,sel=ny,out=y2);

//level3(Add16,And16,f)
Add16(a=x2,b=y2,out=x2ady2);
And16(a=x2,b=y2,out=x2any2);
Mux16(a=x2any2,b=x2ady2,sel=f,out=fout);

//level4(Not16,no)
Not16(in=fout,out=nfout);

Mux16(a=fout,b=nfout,sel=no,out=out,out[0..7]=Highway,out[8..15]=Lowway,out[15]=ng);
Or8Way(in=Highway,out=o81);
Or8Way(in=Lowway,out=o82);
Or(a=o81,b=o82,out=o1);
Not(in=o1,out=zr);

}

ALU-nostaat

// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/02/ALU.hdl
/**

The ALU (Arithmetic Logic Unit).
Computes one of the following functions:
x+y, x-y, y-x, 0, 1, -1, x, y, -x, -y, !x, !y,
x+1, y+1, x-1, y-1, x&y, x|y on two 16-bit inputs,
according to 6 input bits denoted zx,nx,zy,ny,f,no.
In addition, the ALU computes two 1-bit outputs:
if the ALU output == 0, zr is set to 1; otherwise zr is set to 0;
if the ALU output < 0, ng is set to 1; otherwise ng is set to 0.
*/

// Implementation: the ALU logic manipulates the x and y inputs
// and operates on the resulting values, as follows:
// if (zx == 1) set x = 0        // 16-bit constant
// if (nx == 1) set x = !x       // bitwise not
// if (zy == 1) set y = 0        // 16-bit constant
// if (ny == 1) set y = !y       // bitwise not
// if (f == 1)  set out = x + y  // integer 2's complement addition
// if (f == 0)  set out = x & y  // bitwise and
// if (no == 1) set out = !out   // bitwise not
// if (out == 0) set zr = 1
// if (out < 0) set ng = 1
CHIP ALU {
IN

x[16], y[16],  // 16-bit inputs

zx, // zero the x input?
nx, // negate the x input?
zy, // zero the y input?
ny, // negate the y input?
f,  // compute out = x + y (if 1) or x & y (if 0)
no; // negate the out output?
OUT 
    out[16], // 16-bit output
    zr, // 1 if (out == 0), 0 otherwise
    ng; // 1 if (out < 0),  0 otherwise

PARTS:
// Put you code here:
Not16(in=x, out=notx);
And16(a=x,  b=notx, out=z16);      	
Mux16(a=x,  b=z16,  sel=zx, out=x1);  
Not16(in=x1,out=notx1);
Mux16(a=x1, b=notx1, sel=nx, out=x2); 
Mux16(a=y,  b=z16,  sel=zy, out=y1);  
Not16(in=y1,out=noty1);
Mux16(a=y1, b=noty1, sel=ny, out=y2);  
Add16(a=x2, b=y2, out=addxy);         
And16(a=x2, b=y2, out=andxy);
Mux16(a=andxy, b=addxy, sel=f, out=o1); 
Not16(in=o1, out=noto1);  
Mux16(a=o1, b=noto1, sel=no, out=out); 

}