// This file is part of the materials accompanying the book 

// "The Elements of Computing Systems" by Nisan and Schocken, 

// MIT Press. Book site: www.idc.ac.il/tecs

// File name: projects/01/Mux8Way16.hdl



/**

 * 8-way 16-bit multiplexor.  

 * out = a -- if sel=000

 *       b -- if sel=001

 *       c -- if sel=010

 *       d -- if sel=011

 *       ...

 *       h -- if sel=111

 */



/**

  * Note that the numerical value of x[k] is x[k] * 2^k

  * So if sel=100, then sel[0] = 0, sel[1] = 0, and sel[2] = 1

  * This tripped me up because I was reading the bits in the wrong direction!

 */

 

CHIP Mux8Way16 {



    IN  a[16], b[16], c[16], d[16],

        e[16], f[16], g[16], h[16],

        sel[3];



    OUT out[16];



    PARTS: 

    Mux4Way16(a=a, b=b, c=c, d=d, sel=sel[0..1], out=abcd);

    Mux4Way16(a=e, b=f, c=g, d=h, sel=sel[0..1], out=efgh);

    Mux16(a=abcd, b=efgh, sel=sel[2], out=out);

}