get immediate operand when opcode is ADC Immediate

src/instruction.rs

@@ -48,7 +48,9 @@ pub enum Instruction
       //                                  NV BDIZC A X Y S PC M
       //
       //                                | outputs               | inputs
-{ ADC // ADd with Carry................ | NV ...ZC A            = A + M + C
+{ 
+  ADC(i8) // ADd with Carry................ | NV ...ZC A            = A + M + C
+
 , AND // logical AND (bitwise)......... | N. ...Z. A            = A && M
 , ASL // Arithmetic Shift Left......... | N. ...ZC A            = M << 1
 , BCC // Branch if Carry Clear......... | .. .....         PC   = !C

src/machine.rs

@@ -50,27 +50,27 @@ impl Machine {
     	*self = Machine::new();
     }
 
-    pub fn fetch_instruction(&mut self) -> u8  {
+    pub fn fetch_instruction(&mut self) -> i8  {
         let instr = self.memory.get_byte(&self.registers.program_counter);
 
         // Will need smarter logic to fetch the correct number of bytes 
         // for instruction
         self.registers.program_counter = self.registers.program_counter +  AddressDiff(1);
-        instr                    
+        instr as i8
-    }
+    } 
 
-    pub fn decode_instruction(&mut self, raw_instruction: u8) -> Instruction {
+    pub fn decode_instruction(&mut self, raw_instruction: i8) -> Instruction {
         match raw_instruction {
-            0x69 => ADC,
+            0x69 => ADC(self.fetch_instruction()),
             _    => NOP 
         }
     }    
         
     pub fn execute_instruction(&mut self, instruction: Instruction) {
         match instruction {
-            ADC => { 
+            ADC(immediate) => { 
                 println!("executing add with carry");
-                self.add_with_carry(1);
+                self.add_with_carry(immediate);
             },
             NOP => {
                 println!("nop instr");