Added LDA opcode. Tweaking ALU()

src/chip/MOS6502/cpu.js

 }
 
 function LDA(cpu){
-
+ let pmode = [0xA9, 0xA5, 0xB5, null, 0xAD, 0xBD, 0xB9, 0xA1, 0xB1].indexOf(cpu.__op);
+  if (ProcessOp(cpu, pmode) === true){
+    cpu.__op = -1;
+    cpu.__AR = cpu.__opv;
+    cpu.Z = (cpu.__AR === 0);
+    cpu.N = (cpu.__AR >= 0x80);
+  } 
 }
 
 function LDX(cpu){
 }
 
 function ALU(cpu, m, b){
-  let v = 0;
   switch(m){
     case 0: // Addition
       cpu.__AR = (cpu.__AR + b) + ((cpu.C === 1) ? 1 : 0);
-      cpu.C = (v >= 256);
+      //cpu.C = (this.__AR >= 256);
       break;
     case 1: // Subtraction
-      cpu.__AR = (cpu.__AR - b) - ((cpu.C === 0) ? 1 : 0);
-      cpu.C = (v >= 0);
+      cpu.__AR = (cpu.__AR - b) - ((cpu.C === 0) ? 1 : 0); 
+      //cpu.C = (this.__AR >= 0);
+      cpu.__AR += (cpu.__AR < 0) ? 256 : 0;
       break;
-  }
-  cpu.__AR &= 0xFF;
-  cpu.V = (BITM.isOn(cpu.__AR, 7) === BITM.isOn(b, 7)) && (BITM.val(v, 7) !== BITM.val(cpu.__AR, 7));
+  } 
+  cpu.V = (BITM.isOn(cpu.__AR, 7) === BITM.isOn(b, 7)) && (BITM.val(cpu.__AR, 7) !== BITM.val(cpu.__AR, 7));
+  cpu.C = (m === 0) ? (this.__AR >= 256) : (cpu.V === 0);
   cpu.N = BITM.val(cpu.__AR, 7);
+  
+  cpu.__AR &= 0xFF;
   cpu.Z = (cpu.__AR === 0);
   return cpu.__AR;
 }