// 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/03/1/PC.hdl



/**

 * 16-bit counter with load and reset controls.

 *

 * If reset(t-1) then out(t) = 0

 *    else if load(t-1) then out(t) = in(t-1)

 *         else if inc(t-1) then out(t) = out(t-1) + 1 (integer addition)

 *              else out(t) = out(t-1)

 */



CHIP PC {



    IN  in[16], load, inc, reset;

    OUT out[16];



    PARTS:

    Register(in=registerInput, load=true, out=out, out=previousOutput);

    Inc16(in=previousOutput, out=incrementedPreviousOutput);

    Mux16(a=previousOutput, b=incrementedPreviousOutput, sel=inc, out=incOutput);

    Mux16(a=incOutput, b=in, sel=load, out=loadedOutput);

    Mux16(a=loadedOutput, b=false, sel=reset, out=registerInput);

}