By default, do not halt on BRK (#14)

This change introduces a new command line flag, '-b', that cause the
simulator to halt on the `BRK` instruction. By default, however, the
simulator will no longer halt on `BRK`.

As before, this behavior can be toggled in the preferences at run-time.

src/main/java/com/loomcom/symon/Main.java

@@ -53,6 +53,7 @@ public class Main {
         options.addOption(new Option("m", "machine", true, "Specify machine type."));
         options.addOption(new Option("c", "cpu", true, "Specify CPU type."));
         options.addOption(new Option("r", "rom", true, "Specify ROM file."));
+        options.addOption(new Option("b", "brk", false, "Halt on BRK"));
 
         CommandLineParser parser = new DefaultParser();
 
@@ -60,6 +61,7 @@ public class Main {
             CommandLine line = parser.parse(options, args);
             InstructionTable.CpuBehavior cpuBehavior = null;
             String romFile = null;
+            boolean haltOnBreak = false;
 
             if (line.hasOption("machine")) {
                 String machine = line.getOptionValue("machine").toLowerCase(Locale.ENGLISH);
@@ -104,6 +106,10 @@ public class Main {
                 romFile = line.getOptionValue("rom");
             }
 
+            if (line.hasOption("brk")) {
+                haltOnBreak = true;
+            }
+
             while (true) {
                 if (machineClass == null) {
                     Object[] possibilities = {"Symon", "Multicomp", "Simple", "BenEater"};
@@ -132,7 +138,7 @@ public class Main {
                     cpuBehavior = InstructionTable.CpuBehavior.NMOS_6502;
                 }
 
-                final Simulator simulator = new Simulator(machineClass, cpuBehavior, romFile);
+                final Simulator simulator = new Simulator(machineClass, cpuBehavior, romFile, haltOnBreak);
 
                 SwingUtilities.invokeLater(new Runnable() {
                     @Override