timer0 (#32)

Co-authored-by: Darkress <30271678+DarkressX@users.noreply.github.com>
Reviewed-on: darkress/pic16f84-sim#32

de/darkress/pic16f84sim/microcontroller/Timer.java

@@ -0,0 +1,66 @@
+package de.darkress.pic16f84sim.microcontroller;
+
+public class Timer
+{
+    public static int getCyclesToTimerIncrease()
+    {
+        return cyclesToTimerIncrease;
+    }
+
+    public static void setCyclesToTimerIncrease(int cyclesToTimerIncrease)
+    {
+        Timer.cyclesToTimerIncrease = cyclesToTimerIncrease;
+    }
+
+    private static int cyclesToTimerIncrease = 1;
+
+    private static boolean timerEnabled()
+    {
+        return (Memory.getOption() & 0x20) != 0x20;
+    }
+
+    public static void resetTimeToTimerIncrease()
+    {
+        cyclesToTimerIncrease = getPrescalerFactor();
+    }
+
+    private static boolean getPrescalerAsssignment() {
+        return (Memory.getOption() & 0x08) == 0x08;
+    }
+
+    private static int getPrescalerFactor() {
+        final int MULTIPLIER = 2;
+        int prescalerPower = Memory.getOption() & 0x07;
+        int prescaler = (int)Math.pow(2, prescalerPower);
+        if(!getPrescalerAsssignment())
+        {
+            return prescaler * MULTIPLIER;
+        }
+        return prescaler;
+    }
+
+    private static void increaseTimerRegister()
+    {
+        int timerRegister = Memory.getRegister(0x01);
+        timerRegister = (timerRegister + 1) % 256;
+        if(timerRegister == 0) //check for timer Overflow  --> interrupt
+        {
+            System.out.println("Timer Overflow");
+        }
+        Memory.setTimer(timerRegister);
+    }
+
+    public static void increaseTimer()
+    {
+        if(!timerEnabled())
+        {
+            return;
+        }
+        cyclesToTimerIncrease--;
+        if(cyclesToTimerIncrease == 0)
+        {
+            resetTimeToTimerIncrease();
+            increaseTimerRegister();
+        }
+    }
+}