DMux4Way :

了解過 DMux 與 Mux ，這應該不難理解，

只是輸入輸出和選擇位的變化。

sel[1] 決定了 in 在 ab 輸出位還是 cd 輸出位，

sel[0] 在分別確定 a b c d 的值，

只是多次調用 DMux。

| in  | sel  |  a  |  b  |  c  |  d  |
|  0  |  00  |  0  |  0  |  0  |  0  |
|  0  |  01  |  0  |  0  |  0  |  0  |
|  0  |  10  |  0  |  0  |  0  |  0  |
|  0  |  11  |  0  |  0  |  0  |  0  |
|  1  |  00  |  1  |  0  |  0  |  0  |
|  1  |  01  |  0  |  1  |  0  |  0  |
|  1  |  10  |  0  |  0  |  1  |  0  |
|  1  |  11  |  0  |  0  |  0  |  1  |


/**
 * 4-way demultiplexor:
 * {a, b, c, d} = {in, 0, 0, 0} if sel == 00
 *                {0, in, 0, 0} if sel == 01
 *                {0, 0, in, 0} if sel == 10
 *                {0, 0, 0, in} if sel == 11
 */

CHIP DMux4Way 
{
    IN in, sel[2];
    OUT a, b, c, d;

    PARTS:
    DMux(in = in, sel = sel[0], a = a);
    DMux(in = in, sel = sel[1], a = b);
    DMux(in = in, sel = sel[2], a = c);
    DMux(in = in, sel = sel[3], a = d);
}