Fixed conflict with BIT (using BITM for the utility file). Method reset() should now match basic 6502 reset mechanics.

src/chip/MOS6502/cpu.js

@@ -1,7 +1,7 @@
 /*
  * Emulate a basic 6502 (MOS) chip.
  */
-const BIT = require('../../utils/bitman.js');
+const BITM = require('../../utils/bitman.js');
 var Memory = require('../../common/memory.js');
 
 
@@ -319,7 +319,7 @@ function STACK(cpu){
       } else if (cpu.__step === 1){
         cpu.__AR = cpu.__mem.byte;
         cpu.Z = (cpu.__AR === 0);
-        cpu.N = BIT.isOn(cpu.__AR, 7); 
+        cpu.N = BITM.isOn(cpu.__AR, 7); 
       } else if (cpu.__step === 2){ 
         cpu.__SP = (cpu.__SP === 255) ? 0 : cpu.__SP + 1;
         cpu.__op = -1;
@@ -417,8 +417,8 @@ function ALU(cpu, m, b){
       break;
   }
   cpu.__AR &= 0xFF;
-  cpu.V = (BIT.isOn(cpu.__AR, 7) === BIT.isOn(b, 7)) && (BIT.val(v, 7) !== BIT.val(cpu.__AR, 7));
-  cpu.N = BIT.val(cpu.__AR, 7);
+  cpu.V = (BITM.isOn(cpu.__AR, 7) === BITM.isOn(b, 7)) && (BITM.val(v, 7) !== BITM.val(cpu.__AR, 7));
+  cpu.N = BITM.val(cpu.__AR, 7);
   cpu.Z = (cpu.__AR === 0);
   return cpu.__AR;
 }
@@ -467,26 +467,26 @@ class CPU{
 
   // ----------------------------------------
   // Quick Flag Access
-  get N(){return (BIT.isOn(this.__PR, 7)) ? 1 : 0;}
-  set N(n){this.__PR = (n === true || n === 1) ? BIT.set(this.__PR, 7) : BIT.clear(this.__PR, 7);}
+  get N(){return (BITM.isOn(this.__PR, 7)) ? 1 : 0;}
+  set N(n){this.__PR = (n === true || n === 1) ? BITM.set(this.__PR, 7) : BITM.clear(this.__PR, 7);}
 
-  get V(){return (BIT.isOn(this.__PR, 6)) ? 1 : 0;}
-  set V(v){this.__PR = (v === true || v === 1) ? BIT.set(this.__PR, 6) : BIT.clear(this.__PR, 6);}
+  get V(){return (BITM.isOn(this.__PR, 6)) ? 1 : 0;}
+  set V(v){this.__PR = (v === true || v === 1) ? BITM.set(this.__PR, 6) : BITM.clear(this.__PR, 6);}
 
-  get B(){return (BIT.isOn(this.__PR, 4)) ? 1 : 0;}
-  set B(b){this.__PR = (b === true || b === 1) ? BIT.set(this.__PR, 4) : BIT.clear(this.__PR, 4);}
+  get B(){return (BITM.isOn(this.__PR, 4)) ? 1 : 0;}
+  set B(b){this.__PR = (b === true || b === 1) ? BITM.set(this.__PR, 4) : BITM.clear(this.__PR, 4);}
 
-  get D(){return (BIT.isOn(this.__PR, 3)) ? 1 : 0;}
-  set D(d){this.__PR = (d === true || d === 1) ? BIT.set(this.__PR, 3) : BIT.clear(this.__PR, 3);}
+  get D(){return (BITM.isOn(this.__PR, 3)) ? 1 : 0;}
+  set D(d){this.__PR = (d === true || d === 1) ? BITM.set(this.__PR, 3) : BITM.clear(this.__PR, 3);}
   
-  get I(){return (BIT.isOn(this.__PR, 2)) ? 1 : 0;}
-  set I(i){this.__PR = (i === true || i === 1) ? BIT.set(this.__PR, 2) : BIT.clear(this.__PR, 2);}
+  get I(){return (BITM.isOn(this.__PR, 2)) ? 1 : 0;}
+  set I(i){this.__PR = (i === true || i === 1) ? BITM.set(this.__PR, 2) : BITM.clear(this.__PR, 2);}
 
-  get Z(){return (BIT.isOn(this.__PR, 1)) ? 1 : 0;}
-  set Z(z){this.__PR = (z === true || z === 1) ? BIT.set(this.__PR, 1) : BIT.clear(this.__PR, 1);}
+  get Z(){return (BITM.isOn(this.__PR, 1)) ? 1 : 0;}
+  set Z(z){this.__PR = (z === true || z === 1) ? BITM.set(this.__PR, 1) : BITM.clear(this.__PR, 1);}
 
-  get C(){return (BIT.isOn(this.__PR, 0)) ? 1 : 0;}
-  set C(c){this.__PR = (c === true || c === 1) ? BIT.set(this.__PR, 0) : BIT.clear(this.__PR, 0);}
+  get C(){return (BITM.isOn(this.__PR, 0)) ? 1 : 0;}
+  set C(c){this.__PR = (c === true || c === 1) ? BITM.set(this.__PR, 0) : BITM.clear(this.__PR, 0);}
 
   // ----------------------------------------
   // Hardware interrupt triggers. Settable only.
@@ -501,15 +501,21 @@ class CPU{
   }
 
   reset(){
-    // TODO: Read memory address $FFFC - FFFD to find PC start location.
-    // TODO: Reset status registers that get changed on a reset.
+    this.__mem.address = 0xFFFC;
+    this.__PC = this.__mem.byte;
+    this.__mem.address = 0xFFFD;
+    this.__PC |= this.__mem.byte << 8;
+
+    // Disabling the IRQ interrupts is the ONLY flag that must be set
+    // during reset. The others are random.
+    this.I = 1;
   }
 
   // -----------------------------------------
   // Set and Get Memory property.
   get memory(){return this.__mem;}
   set memory(m){
-    if (!(mem instanceof Memory))
+    if (!(m instanceof Memory))
       throw new ValueError("Expected Memory instance object.");
     this.__mem = m;
   }
@@ -531,7 +537,7 @@ class CPU{
             // TODO: Handle NMI Interrupt.
           } else if (this.__irq) {
             this.__irq = false;
-            if (!BIT.isOn(this.__PR, 5)){
+            if (!BITM.isOn(this.__PR, 5)){
               // TODO: Handle IRQ Interrupt.
             }
           } else {