add Memory.hdl

projects/05/Memory.hdl

@@ -0,0 +1,53 @@
+// 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/05/Memory.hdl
+
+/**
+ * The complete address space of the Hack computer's memory,
+ * including RAM and memory-mapped I/O. 
+ * The chip facilitates read and write operations, as follows:
+ *     Read:  out(t) = Memory[address(t)](t)
+ *     Write: if load(t-1) then Memory[address(t-1)](t) = in(t-1)
+ * In words: the chip always outputs the value stored at the memory 
+ * location specified by address. If load==1, the in value is loaded 
+ * into the memory location specified by address. This value becomes 
+ * available through the out output from the next time step onward.
+ * Address space rules:
+ * Only the upper 16K+8K+1 words of the Memory chip are used. 
+ * Access to address>0x6000 is invalid. Access to any address in 
+ * the range 0x4000-0x5FFF results in accessing the screen memory 
+ * map. Access to address 0x6000 results in accessing the keyboard 
+ * memory map. The behavior in these addresses is described in the 
+ * Screen and Keyboard chip specifications given in the book.
+ */
+
+CHIP Memory {
+    IN in[16], load, address[15];
+    OUT out[16];
+
+    PARTS:
+    // Put your code here:
+
+    // 00 00000 0000 0000 <- First RAM16K   Register
+    // 01 11111 1111 1111 <- Last  RAM16K   Register
+    // 10 00000 0000 0000 <- First SCREEN   Register
+    // 10 11111 1111 1111 <- Last  SCREEN   Register
+    // 11 00000 0000 0000 <- One   Keyboard Register
+
+    DMux4Way(in=load, sel=address[13..14], a=toRAM1,
+                                           b=toRAM2,
+                                           c=toScreen,
+                                           d=notNeeded);
+
+    Or(a=toRAM1, b=toRAM2, out=toRAM);
+    RAM16K(in=in, load=toRAM, address=address[0..13], out=fromRAM);
+    Screen(in=in, load=toScreen, address=address[0..12], out=fromScreen);
+    Keyboard(out=fromKeyboard);
+
+    Mux4Way16(sel=address[13..14], out=out, a=fromRAM,
+                                            b=fromRAM,
+                                            c=fromScreen,
+                                            d=fromKeyboard);
+
+}