Chapter 2

HalfAdder

基數個"1"和為"1"，偶數個"1"進位C等於"1"。

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

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

FullAdder

只要輸入有基數個"1"輸出為"1"。

 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:
// Put you code here:
Xor(a=a,b=b,out=o1);
Xor(a=o1,b=c,out=sum);

And(a=b,b=c,out=o2);
And(a=a,b=c,out=o3);
And(a=a,b=b,out=o4);

Or(a=o2,b=o3,out=o5);
Or(a=o5,b=o4,out=carry);
}

Add16

16個全加器。

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

PARTS:
// Put you code here:
FullAdder(a=a[0],b=b[0],sum=out[0],carry=c1);
FullAdder(a=a[1],b=b[1],c=c1,sum=out[1],carry=c2);
FullAdder(a=a[2],b=b[2],c=c2,sum=out[2],carry=c3);
FullAdder(a=a[3],b=b[3],c=c3,sum=out[3],carry=c4);
FullAdder(a=a[4],b=b[4],c=c4,sum=out[4],carry=c5);
FullAdder(a=a[5],b=b[5],c=c5,sum=out[5],carry=c6);
FullAdder(a=a[6],b=b[6],c=c6,sum=out[6],carry=c7);
FullAdder(a=a[7],b=b[7],c=c7,sum=out[7],carry=c8);
FullAdder(a=a[8],b=b[8],c=c8,sum=out[8],carry=c9);
FullAdder(a=a[9],b=b[9],c=c9,sum=out[9],carry=c10);
FullAdder(a=a[10],b=b[10],c=c10,sum=out[10],carry=c11);
FullAdder(a=a[11],b=b[11],c=c11,sum=out[11],carry=c12);
FullAdder(a=a[12],b=b[12],c=c12,sum=out[12],carry=c13);
FullAdder(a=a[13],b=b[13],c=c13,sum=out[13],carry=c14);
FullAdder(a=a[14],b=b[14],c=c14,sum=out[14],carry=c15);
FullAdder(a=a[15],b=b[15],c=c15,sum=out[15],carry=c16);
}

Inc16

IN加1

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

PARTS:
// Put you code here:
Add16(a=in,b[0]=true,out=out);
}

ALU

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:
//zx nx
Mux16(a=x,b=false,sel=zx,out=zdx);
Not16(in=zdx,out=nzdx);
Mux16(a=zdx,b=nzdx,sel=nx,out=ndx);

//zy ny
Mux16(a=y,b=false,sel=zy,out=zdy);
Not16(in=zdy,out=nzdy);
Mux16(a=zdy,b=nzdy,sel=ny,sel=ny,out=ndy);

Add16(a=ndx,b=ndy,out=xaddy);
And16(a=ndx,b=ndy,out=xandy);

//f
Mux16(a=xandy,b=xaddy,sel=f,out=fout);
Not16(in=fout,out=nfout);
//no
Mux16(a=fout,b=nfout,sel=no,out=noout);

//zr
And16(a=noout, b=noout, out[0..7]=outLow, out[8..15]=outHigh); 
Or8Way(in=outLow,out=o1);
Or8Way(in=outHigh,out=o2);
Or(a=o1,b=o2,out=o3);
Not(in=o3,out=zr);

//ng  
And16(a=noout,b=noout,out[15]=ng);
And16(a=noout,b=noout,out=out);

}

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