ALU (Arithmetic and Logic Unit):
The basic building block for a computer is ALU which can perform the basic Arithmetic and logical operations. The Chip creation using the HDL from the basic gates(AND,NOT,MUX,ADDER..etc) gives you the in site knowledge and interest for binary number operations. The below HDL ALU chip can perform 18 operations, potentially which can compute 64.
Follow the course The Elements of Computing Systems
CHIP ALU {
IN // 16-bit inputs:
x[16], y[16],
// Control bits:
zx, // Zero the x input
nx, // Negate the x input
zy, // Zero the y input
ny, // Negate the y input
f, // Function code: 1 for add, 0 for and
no; // Negate the out output
OUT // 16-bit output
out[16],
// ALU output flags
zr, // 1 if out=0, 0 otherwise
ng; // 1 if out<0, 0 otherwise
PARTS:
Mux16(a[0..15]=x[0..15], b[0..15]=false, sel=zx, out[0..15]=x1);
Mux16(a[0..15]=y[0..15], b[0..15]=false, sel=zy, out[0..15]=y1);
Not16(in[0..15]=x1, out[0..15]=notx1);
Not16(in[0..15]=y1, out[0..15]=noty1);
Mux16(a[0..15]=x1, b[0..15]=notx1, sel=nx, out[0..15]=x2);
Mux16(a[0..15]=y1, b[0..15]=noty1, sel=ny, out=y2);
And16(a[0..15]=x2, b[0..15]=y2, out=Andxy);
Add16(a[0..15]=x2, b[0..15]=y2, out=Addxy);
Mux16(a[0..15]=Andxy, b[0..15]=Addxy, sel=f, out=x3);
Not16(in[0..15]=x3, out=notx3);
Mux16(a[0..15]=x3, b[0..15]=notx3, sel=no, out[0]=ou1,out[1]=ou2,out[2]=ou3,out[3]=ou4,out[4]=ou5,out[5]=ou6,out[6]=ou7,out[7]=ou8,out[8]=ou9,out[9]=ou10,out[10]=ou11,out[11]=ou12,out[12]=ou13,out[13]=ou14,out[14]=ou15,out[15]=ou16);
Or(a=ou1, b=ou2,out= out1);
Or(a=ou2,b= out1,out= out2);
Or(a=ou3,b= out2,out= out3);
Or(a=ou4,b= out3,out= out4);
Or(a=ou5,b= out4,out= out5);
Or(a=ou6,b= out5,out= out6);
Or(a=ou7,b= out6,out= out7);
Or(a=ou8,b= out7,out= out8);
Or(a=ou9,b= out8,out= out9);
Or(a=ou10,b= out9,out= out10);
Or(a=ou11,b= out10,out= out11);
Or(a=ou12,b= out11,out= out12);
Or(a=ou13,b= out12,out= out13);
Or(a=ou14,b= out13,out= out14);
Or(a=ou15,b= out14,out= out15);
Or(a=ou16,b= out15,out= notzr);
Not(in=notzr,out=zr);
And(a=ou16,b=true,out=ng);
And(a=ou1,b=true,out=out[0]);
And(a=ou2,b=true,out=out[1]);
And(a=ou3,b=true,out=out[2]);
And(a=ou4,b=true,out=out[3]);
And(a=ou5,b=true,out=out[4]);
And(a=ou6,b=true,out=out[5]);
And(a=ou7,b=true,out=out[6]);
And(a=ou8,b=true,out=out[7]);
And(a=ou9,b=true,out=out[8]);
And(a=ou10,b=true,out=out[9]);
And(a=ou11,b=true,out=out[10]);
And(a=ou12,b=true,out=out[11]);
And(a=ou13,b=true,out=out[12]);
And(a=ou14,b=true,out=out[13]);
And(a=ou15,b=true,out=out[14]);
And(a=ou16,b=true,out=out[15]);
}
