PC.hdl

// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/3/a/PC.hdl
/**
 * A 16-bit counter.
 * if      reset(t): out(t+1) = 0
 * else if load(t):  out(t+1) = in(t)
 * else if inc(t):   out(t+1) = out(t) + 1
 * else              out(t+1) = out(t)
 */
CHIP PC {
    IN in[16], reset, load, inc;
    OUT out[16];
    
    PARTS:
    Or(a=inc,b=reset,out=sel);
    Or(a=sel,b=load,out=slt);
    Inc16(in=in1,out=in2);
    Mux16(a=in,b=out5,sel=inc,out=in1);

    Mux16(a=in,b=in2,sel=inc,out=out2);

    Mux16(a=out2,b=in,sel=load,out=out3);

    Mux16(a=out3,b=false,sel=reset,out=out4);

    Register(in=out4,load=slt,out=out5);

    And16(a=out5,b=out5,out=out);
}