Split PIA into PIA/VIA6522

src/main/java/com/loomcom/symon/devices/Pia.java

@@ -23,45 +23,19 @@
 
 package com.loomcom.symon.devices;
 
-import com.loomcom.symon.exceptions.MemoryAccessException;
 import com.loomcom.symon.exceptions.MemoryRangeException;
 
-public class Pia extends Device {
+public abstract class Pia extends Device {
-    public static final int PIA_SIZE = 16;
 
-    private static final int ORB = 0;
+    private final String name;
-    private static final int ORA = 1;
-    private static final int DDRB = 2;
-    private static final int DDRA = 3;
-    private static final int T1C_L = 4;
-    private static final int T1C_H = 5;
-    private static final int T1L_L = 6;
-    private static final int T1L_H = 7;
-    private static final int T2C_L = 8;
-    private static final int T2C_H = 9;
-    private static final int SR = 10;
-    private static final int ACR = 11;
-    private static final int PCR = 12;
-    private static final int IFR = 13;
-    private static final int IER = 14;
-    private static final int ORA_H = 15;
 
-    public Pia(int address) throws MemoryRangeException {
+    public Pia(int startAddress, int endAddress, String name) throws MemoryRangeException {
-      super(address, address + PIA_SIZE - 1, "PIA");
+        super(startAddress, endAddress, name);
-    }
+        this.name = name;
-
-    @Override
-    public void write(int address, int data) throws MemoryAccessException {
-        ; // No-Op
-    }
-
-    @Override
-    public int read(int address) throws MemoryAccessException {
-        return 0;
     }
 
     @Override
     public String toString() {
-        return null;
+        return name;
     }
 }

src/main/java/com/loomcom/symon/devices/Via6522.java

@@ -0,0 +1,90 @@
+package com.loomcom.symon.devices;
+
+import com.loomcom.symon.exceptions.MemoryAccessException;
+import com.loomcom.symon.exceptions.MemoryRangeException;
+
+/**
+ * Very basic implementation of a MOS 6522 VIA.
+ *
+ * TODO: Implement timers as threads.
+ */
+public class Via6522 extends Pia {
+    public static final int VIA_SIZE = 16;
+
+    enum Register {
+        ORB, ORA, DDRB, DDRA, T1C_L, T1C_H, T1L_L, T1L_H,
+        T2C_L, T2C_H, SR, ACR, PCR, IFR, IER, ORA_H
+    }
+
+    // Ports A and B
+    private char[] portData = {0, 0};
+    private char[] portDirections = {0, 0};
+
+    public Via6522(int address) throws MemoryRangeException {
+        super(address, address + VIA_SIZE - 1, "MOS 6522 VIA");
+    }
+
+    @Override
+    public void write(int address, int data) throws MemoryAccessException {
+        Register[] registers = Register.values();
+
+        if (address >= registers.length) {
+            throw new MemoryAccessException("Unknown register: " + address);
+        }
+
+        Register r = registers[address];
+
+        switch (r) {
+            case ORA:
+            case ORB:
+            case DDRA:
+            case DDRB:
+            case T1C_L:
+            case T1C_H:
+            case T1L_L:
+            case T1L_H:
+            case T2C_L:
+            case T2C_H:
+            case SR:
+            case ACR:
+            case PCR:
+            case IFR:
+            case IER:
+            case ORA_H:
+            default:
+        }
+    }
+
+    @Override
+    public int read(int address) throws MemoryAccessException {
+        Register[] registers = Register.values();
+
+        if (address >= registers.length) {
+            throw new MemoryAccessException("Unknown register: " + address);
+        }
+
+        Register r = registers[address];
+
+        switch (r) {
+            case ORA:
+            case ORB:
+            case DDRA:
+            case DDRB:
+            case T1C_L:
+            case T1C_H:
+            case T1L_L:
+            case T1L_H:
+            case T2C_L:
+            case T2C_H:
+            case SR:
+            case ACR:
+            case PCR:
+            case IFR:
+            case IER:
+            case ORA_H:
+            default:
+        }
+
+        return 0;
+    }
+}

src/main/java/com/loomcom/symon/machines/SymonMachine.java

@@ -26,11 +26,7 @@ package com.loomcom.symon.machines;
 
 import com.loomcom.symon.Bus;
 import com.loomcom.symon.Cpu;
-import com.loomcom.symon.devices.Acia;
+import com.loomcom.symon.devices.*;
-import com.loomcom.symon.devices.Acia6551;
-import com.loomcom.symon.devices.Crtc;
-import com.loomcom.symon.devices.Memory;
-import com.loomcom.symon.devices.Pia;
 import com.loomcom.symon.exceptions.MemoryRangeException;
 import java.io.File;
 import java.util.logging.Logger;
@@ -78,7 +74,7 @@ public class SymonMachine implements Machine {
         this.bus = new Bus(BUS_BOTTOM, BUS_TOP);
         this.cpu = new Cpu();
         this.ram = new Memory(MEMORY_BASE, MEMORY_BASE + MEMORY_SIZE - 1, false);
-        this.pia = new Pia(PIA_BASE);
+        this.pia = new Via6522(PIA_BASE);
         this.acia = new Acia6551(ACIA_BASE);
         this.crtc = new Crtc(CRTC_BASE, ram);