timer0 (#32)

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

de/darkress/pic16f84sim/microcontroller/Cycles.java

@@ -3,9 +3,10 @@ package de.darkress.pic16f84sim.microcontroller;
 public class Cycles {
     private static int cycles = 0;
 
-    public static void addToCycles(int increase)
+    public static void incCycles()
     {
-        cycles += increase;
+        Timer.increaseTimer();
+        cycles++;
     }
 
     public static int getCycles() {

de/darkress/pic16f84sim/microcontroller/Memory.java

@@ -4,6 +4,13 @@ import java.util.Arrays;
 
 public class Memory
 {
+    public static void initMemory()
+    {
+        Memory.memory[0x81] = 0xFF; //Option
+        Memory.memory[0x85] = 0x1F; //TrisA
+        Memory.memory[0x86] = 0xFF; //TrisB
+        Memory.setRegister(0x03, 0x18); //Status
+    }
     private static final int MEMORY_SIZE = 0xFF;  //Addressable Memory
     public static int workingRegister = 0;
     private static final int[] memory = new int[MEMORY_SIZE];
@@ -47,12 +54,19 @@ public class Memory
             setDataFromIndirectAddress(indirectAddress, data);
             return;
         }
+        if(address == 0x01) //Reset PrescalerCounter if change on Option or Timer Register
+        {
+            Timer.resetTimeToTimerIncrease();
+            Timer.setCyclesToTimerIncrease(Timer.getCyclesToTimerIncrease() - 1); //Decrease by one to account for
+            // this command execution
+        }
         if((Arrays.stream(bank0UniqueSpecialRegister).anyMatch(x -> x == address)) && getRegisterBank() == 0)
         {
             memory[address] = data;
             return;
         }
-        if((Arrays.stream(bank1UniqueSpecialRegister).anyMatch(x -> x == address)) && getRegisterBank() == 1)
+        if((Arrays.stream(bank0UniqueSpecialRegister).anyMatch(x -> x == address)) && getRegisterBank() == 1) //bank0
+            // because of 7 Bit address
         {
             memory[address + 128] = data;
             return;
@@ -72,6 +86,12 @@ public class Memory
 
     private static void setDataFromIndirectAddress(int address, int data)
     {
+        if(address == 0x81 || address == 0x01) //Reset PrescalerCounter if change on Option or Timer Register
+        {
+            Timer.resetTimeToTimerIncrease();
+            Timer.setCyclesToTimerIncrease(Timer.getCyclesToTimerIncrease() - 1); //Decrease by one to account for
+            // this command execution
+        }
         if((Arrays.stream(bank0UniqueSpecialRegister).anyMatch(x -> x == address)) || (Arrays.stream(bank1UniqueSpecialRegister).anyMatch(x -> x == address)))
         {
             memory[address] = data;
@@ -79,10 +99,6 @@ public class Memory
         }
         memory[address % 128] = data; // else: Registers.Registers which are mapped
         memory[address % 128 + 128] = data; //Ensure data is written to both banks to simulate mapping
-        if(address == 0x2) //Check if PCL is destination
-        {
-            ProgramCounter.loadPc();
-        }
     }
 
     private static int getRegisterBank()
@@ -121,6 +137,21 @@ public class Memory
         memory[0x8A] = data & 0x1F;
     }
 
+    public static int getOption()
+    {
+        return memory[0x81];
+    }
+
+    public static int getTimer()
+    {
+        return memory[0x01];
+    }
+
+    public static void setTimer(int data)
+    {
+        memory[0x01] = data;
+    }
+
     public static boolean getZeroBit()
     {
         return (memory[0x03] & 0x04) == 0x04;

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();
+        }
+    }
+}