Preliminary implementations for memory modules and a memory mapping controller (MMC).

chip/memory.js

+
+
+class Memory{
+  constructor(size, ro){
+    this.__ro = (ro === true);
+    this.__map = null;
+    this.__addr = 0;
+    if (size > 0){
+      this.__map = new Uint8Array(size);
+    }
+  }
+
+  get size(){return (this.__map) ? this.__map.length : 0;}
+
+  get address(){return this.__addr;}
+  set address(a){
+    if (this.__map)
+      this.__addr = Math.min(this.__map.length, Math.max(0, a));
+  }
+
+  get byte(){return (this.__map) ? this.__map[this.__addr] : -1;}
+  set byte(b){
+    if (!this.__ro && this.__map)
+      this.__map[this.__addr] = b;
+  }
+
+  sysStore(address, data){
+    if (this.__map){
+      let dc = data;
+      if (address < 0 || address >= this.__map.length)
+        throw new RangeError("Memory address out of range.");
+      if (this.__map.length - address < dc.length)
+        dc = dc.slice(0, this.__map.length - address);
+      this.__map.set(address, dc);
+      return dc.length;
+    }
+  }
+}
+
+
+module.exports = Memory;

chip/mmc.js

+
+var Memory = require('chip/memory');
+
+class Bank{
+  constructor(mem){
+    this.__mem = [mem];
+    this.__idx = 0;
+  }
+
+  get mem(){return this.__mem[this.__idx];}
+
+  get idx(){return this.__idx;}
+  set idx(i){
+    if (i >= 0 && i < this.__mem.length)
+      this.__idx = i;
+  }
+
+  addMemModule(mem){
+    if (!(mem instanceof Memory))
+      throw new ValueError("Only Memory instances can be added to MMC Banks.");
+    if (this.__mem.length >= 4)
+      throw new RangeError("Bank handling maximum memory modules.");
+    if (this.__mem.length > 0 && mem.size !== this.__mem[0].size)
+      throw new RangeError("Memory module does not match size of already connected memory modules on this bank.");
+    this.__mem.push(mem);
+  }
+}
+
+class MMC{
+  constructor(){
+    this.__banks = [];
+  }
+
+  get size(){
+    return this.__banks.reduce((acc, b)=>{
+      acc += b.mem.size;
+    }, 0);
+  }
+
+  get banks(){return this.__banks.length;}
+
+  // TODO: Add a get/set for the memory address. This should handle banking and memory address offsets.
+  // TODO: Add a get/set for memory data at the current address.
+  // TODO: Add method for adding memory modules}
+  // TODO: Add a connection between a memory address and the triggering of bank switching.
+}
+
+module.exports = MMC;