// 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: tools/builtIn/DRegister.hdl

/**
 * A 16-Bit register called "D Register". 
 * If load[t-1]=1 then out[t] = in[t-1]
 * else out does not change (out[t] = out[t-1])
 *
 * This built-in chip implementation has the side effect of 
 * providing a GUI representation of a 16-bit register
 * called "D register" (typically used to store data).
 */

CHIP DRegister {

    IN  in[16], load;
    OUT out[16];

    BUILTIN DRegister;
    CLOCKED in, load;
}