From 9542deeb483a00b6fabed7574720926ce97d7511 Mon Sep 17 00:00:00 2001
From: Frederick Yin <fkfd@fkfd.me>
Date: Tue, 16 Aug 2022 11:54:23 +0800
Subject: Projects, 01-06 completed

---
 projects/05/Memory.hdl | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 projects/05/Memory.hdl

(limited to 'projects/05/Memory.hdl')

diff --git a/projects/05/Memory.hdl b/projects/05/Memory.hdl
new file mode 100644
index 0000000..c551d74
--- /dev/null
+++ b/projects/05/Memory.hdl
@@ -0,0 +1,43 @@
+// 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:
+    // RAM16K
+    Not(in=address[14], out=notaddr14);
+    And(a=notaddr14, b=load, out=loadRAM16K);
+    RAM16K(in=in, load=loadRAM16K, address=address[0..13], out=outRAM16K);
+    // Screen
+    Not(in=address[13], out=notaddr13);
+    And(a=notaddr13, b=address[14], out=screenaddr);
+    And(a=screenaddr, b=load, out=loadScreen);
+    Screen(in=in, load=loadScreen, address=address[0..12], out=outScreen);
+    // Keyboard
+    Keyboard(out=outKeyboard);
+    Mux16(a=outScreen, b=outKeyboard, sel=address[13], out=scrkbd);
+    Mux16(a=outRAM16K, b=scrkbd, sel=address[14], out=out);
+}
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