// 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/b/RAM512.hdl

/**
 * Memory of 512 registers, each 16 bit-wide. Out holds the value
 * stored at the memory location specified by address. If load==1, then
 * the in value is loaded into the memory location specified by address
 * (the loaded value will be emitted to out from the next time step onward).
 */

CHIP RAM512 {
    IN in[16], load, address[9];
    OUT out[16];

    PARTS:
    // To flip things here, let's use the
    // LSB to address the RAM64 modules
    DMux8Way(in=load, sel=address[0..2],
      a=load1,
      b=load2,
      c=load3,
      d=load4,
      e=load5,
      f=load6,
      g=load7,
      h=load8);

    // We use the MSB to index inside the RAM64s
    RAM64(in=in, load=load1, address=address[3..8], out=out1);
    RAM64(in=in, load=load2, address=address[3..8], out=out2);
    RAM64(in=in, load=load3, address=address[3..8], out=out3);
    RAM64(in=in, load=load4, address=address[3..8], out=out4);
    RAM64(in=in, load=load5, address=address[3..8], out=out5);
    RAM64(in=in, load=load6, address=address[3..8], out=out6);
    RAM64(in=in, load=load7, address=address[3..8], out=out7);
    RAM64(in=in, load=load8, address=address[3..8], out=out8);

    // Now we use the LSB again to pick the correct RAM output
    Mux8Way16(
      a=out1,
      b=out2,
      c=out3,
      d=out4,
      e=out5,
      f=out6,
      g=out7,
      h=out8,
      sel=address[0..2], out=out);
}