Branches coded.

src/chip/MOS6502/cpu.js

@@ -22,7 +22,45 @@ function BIT(cpu){
 }
 
 function BRANCH(cpu){
-
+  switch(cpu.__step){
+    case 0:
+      cpu.__mem.address = this.__PC;
+      let v = cpu.__mem.byte;
+      cpu.__opv = v;
+      break;
+    case 1:
+      let branch = false;
+      switch(cpu.__op){
+        case 0x10: // BPL
+          branch = (cpu.N === 0); break;
+        case 0x30: // BMI
+          branch = (cpu.N === 1); break;
+        case 0x50: // BVC
+          branch = (cpu.V === 0); break;
+        case 0x70: // BVS
+          branch = (cpu.V === 1); break;
+        case 0x90: // BCC
+          branch = (cpu.C === 0); break;
+        case 0xB0: // BCS
+          branch = (cpu.C === 1); break;
+        case 0xD0: // BNE
+          branch = (cpu.Z === 0); break;
+        case 0xF0: // BEQ
+          branch = (cpu.Z === 1); break;
+      }
+      if (branch === false)
+        PCUp(cpu, 1);
+    case 2:
+      if (cpu.__step === 2){
+        if (cpu.__opv > 128){
+          PCDown(cpu, 255 - cpu.__opv);
+        } else {
+          PCUp(cpu, cpu.__opv);
+        }
+      }
+      cpu.__op = -1;
+  }
+  cpu.__step += 1;
 }
 
 function BRK(cpu){
@@ -201,12 +239,22 @@ class CPU{
   // ----------------------------------------
   // CPU Registers. Here for debug purposes.
   get PC(){return this.__PC;}
-  get P(){return this.__SR;}
+  get P(){return this.__PR;}
   get X(){return this.__XR;}
   get Y(){return this.__YR;}
   get A(){return this.__AR;}
 
   // ----------------------------------------
+  // Quick Flag Access
+  get N(){return (BIT.isOn(this.__PR, 0)) ? 1 : 0;}
+  get V(){return (BIT.isOn(this.__PR, 1)) ? 1 : 0;}
+  get B(){return (BIT.isOn(this.__PR, 3)) ? 1 : 0;}
+  get D(){return (BIT.isOn(this.__PR, 4)) ? 1 : 0;}
+  get I(){return (BIT.isOn(this.__PR, 5)) ? 1 : 0;}
+  get Z(){return (BIT.isOn(this.__PR, 6)) ? 1 : 0;}
+  get C(){return (BIT.isOn(this.__PR, 7)) ? 1 : 0;}
+
+  // ----------------------------------------
   // Hardware interrupt triggers. Settable only.
   set NMI(n){
     this.__nmi = (n === true);
@@ -254,6 +302,7 @@ class CPU{
             }
           } else {
             this.__step = 0;
+            this.__mem.address = this.__PC;
             this.__op = this.__mem.byte;
             PCUp(this, 1);
           }