Nand2tetris –Project 2

构建半加器全加器等芯片,利用这些和project 1的芯片构成一个简单ALU

/**
 * Computes the sum of two bits.
 */

CHIP HalfAdder {
    IN a, b;    // 1-bit inputs
    OUT sum,    // Right bit of a + b 
        carry;  // Left bit of a + b

    PARTS:
    And(a=a, b=b, out=carry);
    Xor(a=a, b=b, out=sum);
    
    // Put you code here:
}




/**
 * Computes the sum of three bits.
 */

CHIP FullAdder {
    IN a, b, c;  // 1-bit inputs
    OUT sum,     // Right bit of a + b + c
        carry;   // Left bit of a + b + c

    PARTS:
    HalfAdder(a=a, b=b, sum=s1, carry=c1);
    HalfAdder(a=s1, b=c, sum=sum, carry=c2);
    Or(a=c1, b=c2, out=carry);
    // Put you code here:
}


/**
 * Adds two 16-bit values.
 * The most significant carry bit is ignored.
 */

CHIP Add16 {
    IN a[16], b[16];
    OUT out[16];

    PARTS:
    HalfAdder(a=a[0], b=b[0], sum=out[0], carry=c0);
    FullAdder(a=a[1], b=b[1], c=c0, sum=out[1], carry=c1);
    FullAdder(a=a[2], b=b[2], c=c1, sum=out[2], carry=c2);
    FullAdder(a=a[3], b=b[3], c=c2, sum=out[3], carry=c3);
    FullAdder(a=a[4], b=b[4], c=c3, sum=out[4], carry=c4);
    FullAdder(a=a[5], b=b[5], c=c4, sum=out[5], carry=c5);
    FullAdder(a=a[6], b=b[6], c=c5, sum=out[6], carry=c6);
    FullAdder(a=a[7], b=b[7], c=c6, sum=out[7], carry=c7);
    FullAdder(a=a[8], b=b[8], c=c7, sum=out[8], carry=c8);
    FullAdder(a=a[9], b=b[9], c=c8, sum=out[9], carry=c9);
    FullAdder(a=a[10], b=b[10], c=c9, sum=out[10], carry=c10);
    FullAdder(a=a[11], b=b[11], c=c10, sum=out[11], carry=c11);
    FullAdder(a=a[12], b=b[12], c=c11, sum=out[12], carry=c12);
    FullAdder(a=a[13], b=b[13], c=c12, sum=out[13], carry=c13);
    FullAdder(a=a[14], b=b[14], c=c13, sum=out[14], carry=c14);
    FullAdder(a=a[15], b=b[15], c=c14, sum=out[15], carry=c15);
   // Put you code here:
}
/**
 * 16-bit incrementer:
 * out = in + 1 (arithmetic addition)
 */

CHIP Inc16 {
    IN in[16];
    OUT out[16];

    PARTS:
    Add16(a=in, b[1..15]=false, b[0]=true, out=out);
    
}

/**
 * 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:
    Mux16(a=x, b=false, sel=zx, out=x1); //zx
    Not16(in=x1, out=nx1);//nx
    Mux16(a=x1, b=nx1, sel=nx, out=x2);

    Mux16(a=y, b=false, sel=zy, out=y1);//zy
    Not16(in=y1, out=ny1);//ny
    Mux16(a=y1, b=ny1, sel=ny, out=y2);
    And16(a=x2, b=y2, out=o1);//f
    Add16(a=x2, b=y2, out=o2);
    Mux16(a=o1, b=o2, sel=f, out=out1);
    Not16(in=out1, out=nout1);//n
    Mux16(a=out1, b=nout1, sel=no, out=out,out=oo);
    Mux16(a=oo, b=false, sel=false, out[0..7]=aa,out[8..15]=bb);
    Or8Way(in=aa, out=aaa);
    Or8Way(in=bb, out=bbb);
    Or(a=aaa, b=bbb, out=nzr);
    Not(in=nzr, out=zr);
    And(a=aaa, b=bbb, out=ng);
   // Put you code here:
}