implemented return instruction; Fixed Bug in Stack.pop()

Co-authored-by: Darkress <30271678+DarkressX@users.noreply.github.com>
Reviewed-on: darkress/pic16f84-sim#3

de/darkress/pic16f84sim/Main.java

@@ -12,14 +12,14 @@ class Main
     public static void main(String[] args) {
 
         ArrayList<Command> program = new ArrayList<>();
-        Memory.workingRegister = 0xAA;
+        int input1 = 0x27FF;
-        int input1 = 0x2FFF;
+        program.add(CommandDecoder.decode(0x3011));
-        program.add(CommandDecoder.decode(input1));
+        program.add(CommandDecoder.decode(0x2003));
-
+        program.add(CommandDecoder.decode(0x3022));
-        Memory.setPCLATH(0xFF);
+        program.add(CommandDecoder.decode(0x0008));
-        program.get(0).execute();
+        while(true)
-
+        {
-        //ProgramCounter.incPC();
+            program.get(ProgramCounter.getPc()).execute();
-
+        }
     }
 }

de/darkress/pic16f84sim/commands/Call.java

@@ -0,0 +1,21 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+import de.darkress.pic16f84sim.microcontroller.Stack;
+
+public class Call extends CommandUtils implements Command
+{
+    private final int literal;
+
+    public Call(int input)
+    {
+        literal = input & 0x07FF;
+    }
+
+    @Override
+    public void execute()
+    {
+        Stack.push(ProgramCounter.getPc() + 1);
+        ProgramCounter.setPcFrom11BitLiteral(literal);
+    }
+}

de/darkress/pic16f84sim/commands/Goto.java

@@ -1,6 +1,5 @@
 package de.darkress.pic16f84sim.commands;
 
-import de.darkress.pic16f84sim.microcontroller.Memory;
 import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
 
 public class Goto extends CommandUtils implements Command
@@ -15,6 +14,6 @@ public class Goto extends CommandUtils implements Command
     @Override
     public void execute()
     {
-        ProgramCounter.setPcForGotoCall(literal);
+        ProgramCounter.setPcFrom11BitLiteral(literal);
     }
 }

de/darkress/pic16f84sim/commands/Return.java

@@ -0,0 +1,13 @@
+package de.darkress.pic16f84sim.commands;
+
+import de.darkress.pic16f84sim.microcontroller.ProgramCounter;
+import de.darkress.pic16f84sim.microcontroller.Stack;
+
+public class Return extends CommandUtils implements Command
+{
+    @Override
+    public void execute()
+    {
+        ProgramCounter.setPcFrom11BitLiteral(Stack.pop());
+    }
+}

de/darkress/pic16f84sim/decoder/CommandDecoder.java

@@ -100,8 +100,7 @@ public class CommandDecoder
         switch(input & 0x3800)
         {
             case 0x2000:
-                //call();
+                return new Call(input);
-                break;
             case 0x2800:
                 return new Goto(input);
         }
@@ -132,8 +131,7 @@ public class CommandDecoder
 
         if (input == 0x0008)
         {
-            //return();
+            return new Return();
-            //This is the function name. Do not mistake this for a normal return!
         }
 
         if (input == 0x0063)

de/darkress/pic16f84sim/microcontroller/ProgramCounter.java

@@ -11,7 +11,7 @@ public class ProgramCounter
         return pc;
     }
 
-    public static void setPcForGotoCall(int data)
+    public static void setPcFrom11BitLiteral(int data)
     {
         int pcl = data & 0x00FF;
         int pch = Memory.getPCLATH();

de/darkress/pic16f84sim/microcontroller/Stack.java

@@ -14,9 +14,8 @@ public class Stack
 
     public static int pop()
     {
-        int tmp = stack[stackPointer];
         pointPrevious();
-        return tmp;
+        return stack[stackPointer];
     }
 
     public static int peek()