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Simulator is just about ready for real-world testing now. Added a simulated

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MOS6551 ACIA at address $C000 which does buffered input and output via the
console. Updated the README with a bit more documentation, and bumped the
version number to 0.1 because I'm impatient.
This commit is contained in:
Seth J. Morabito committed 2010-01-20 18:19:39 -08:00
1 parent 596d05e398
commit 00ab8cd9ff
10 files changed
+749 -124
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src/main/java/com/loomcom/symon/Simulator.java
+134 -58
View File
@@ -21,24 +21,50 @@ public class Simulator {
* correct IO devices.
*/
private Bus bus;
/**
* The ACIA, used for charater in/out.
*
* By default, the simulator uses base address c000 for the ACIA.
*/
private Acia acia;
private BufferedReader in;
private BufferedWriter out;
/* If true, trace execution of the CPU */
private boolean trace = false;
private int nextExamineAddress = 0;
private static final int BUS_BOTTOM = 0x0000;
private static final int BUS_TOP = 0xffff;
private static final int ACIA_BASE = 0xc000;
private static final int MEMORY_BASE = 0x0000;
private static final int MEMORY_SIZE = 0xc000; // 48 KB
private static final int ROM_BASE = 0xe000;
private static final int ROM_SIZE = 0x2000; // 8 KB
public Simulator() throws MemoryRangeException {
cpu = new Cpu();
bus = new Bus(0x0000, 0xffff);
this.bus = new Bus(BUS_BOTTOM, BUS_TOP);
this.cpu = new Cpu();
this.acia = new Acia(ACIA_BASE);
bus.addCpu(cpu);
bus.addDevice(new Memory(0x0000, 0x10000));
bus.addDevice(new Memory(MEMORY_BASE, MEMORY_SIZE, false));
bus.addDevice(acia);
// TODO: This should be read-only memory. Add a method
// to allow one-time initialization of ROM with a loaded
// ROM binary file.
bus.addDevice(new Memory(ROM_BASE, ROM_SIZE, false));
this.in = new BufferedReader(new InputStreamReader(System.in));
this.out = new BufferedWriter(new OutputStreamWriter(System.out));
}
public void run() throws MemoryAccessException {
public void run() throws MemoryAccessException, FifoUnderrunException {
try {
greeting();
prompt();
@@ -57,12 +83,14 @@ public class Simulator {
System.exit(1);
}
}
/**
* Dispatch the command.
*/
public void dispatch(String commandLine)
throws MemoryAccessException, IOException, CommandFormatException {
public void dispatch(String commandLine) throws MemoryAccessException,
IOException,
CommandFormatException,
FifoUnderrunException {
Command c = new Command(commandLine);
String cmd = c.getCommand();
if (cmd != null) {
@@ -72,7 +100,7 @@ public class Simulator {
doGetState();
} else if (cmd.startsWith("se")) {
doSet(c);
} else if (cmd.startsWith("r")) {
} else if (cmd.startsWith("r")) {
doReset();
} else if (cmd.startsWith("e")) {
doExamine(c);
@@ -93,7 +121,7 @@ public class Simulator {
}
}
}
public void doHelp(Command c) throws IOException {
writeLine("Symon 6502 Simulator");
writeLine("");
@@ -102,16 +130,16 @@ public class Simulator {
writeLine("Note that 'go' clears the BREAK processor status flag.");
writeLine("");
writeLine("h Show this help file.");
writeLine("g [address] [steps] Start running at address, or at PC.");
writeLine("e [start] [end] Examine memory at PC, start, or start-end.");
writeLine("d <address> <data> Deposit data into address.");
writeLine("f <start> <end> <data> Fill memory with data.");
writeLine("reset Reset simulator.");
writeLine("set {pc,a,x,y} [data] Set register to data value.");
writeLine("stat Show CPU state.");
writeLine("step [address] Step once, optionally starting at address.");
writeLine("trace Toggle trace.");
writeLine("load <file> <address> Load binary file at address.");
writeLine("g [address] [steps] Start running at address, or at PC.");
writeLine("step [address] Step once, optionally starting at address.");
writeLine("stat Show CPU state.");
writeLine("reset Reset simulator.");
writeLine("trace Toggle trace.");
writeLine("q (or Control-D) Quit.\n");
}
@@ -119,25 +147,26 @@ public class Simulator {
writeLine(cpu.toString());
writeLine("Trace is " + (trace ? "on" : "off"));
}
public void doLoad(Command c) throws IOException, MemoryAccessException,
CommandFormatException {
public void doLoad(Command c) throws IOException,
MemoryAccessException,
CommandFormatException {
if (c.numArgs() != 2) {
throw new CommandFormatException("load <file> <address>");
}
File binFile = new File(c.getArg(0));
int address = stringToWord(c.getArg(1));
if (!binFile.exists()) {
throw new CommandFormatException("File '" + binFile +
"' does not exist.");
}
writeLine("Loading file '" + binFile + "' at address " +
String.format("%04x", address) + "...");
int bytesLoaded = 0;
FileInputStream fis = new FileInputStream(binFile);
try {
@@ -149,13 +178,13 @@ public class Simulator {
} finally {
fis.close();
}
writeLine("Loaded " + bytesLoaded + " (" +
String.format("$%04x", bytesLoaded) + ") bytes");
}
public void doSet(Command c) throws MemoryAccessException,
CommandFormatException {
public void doSet(Command c) throws MemoryAccessException,
CommandFormatException {
if (c.numArgs() != 2) {
throw new CommandFormatException("set {a, x, y, pc} <value>");
}
@@ -177,9 +206,10 @@ public class Simulator {
throw new CommandFormatException("Illegal address");
}
}
public void doExamine(Command c) throws IOException, MemoryAccessException,
CommandFormatException {
public void doExamine(Command c) throws IOException,
MemoryAccessException,
CommandFormatException {
try {
if (c.numArgs() == 2) {
int startAddress = stringToWord(c.getArgs()[0]);
@@ -206,15 +236,15 @@ public class Simulator {
bus.read(nextExamineAddress)));
nextExamineAddress++;
} else {
throw new CommandFormatException("e [start [end]]");
throw new CommandFormatException("e [start [end]]");
}
} catch (NumberFormatException ex) {
throw new CommandFormatException("Illegal Address");
}
}
public void doDeposit(Command c) throws MemoryAccessException,
CommandFormatException {
CommandFormatException {
if (c.numArgs() != 2) {
throw new CommandFormatException("d [address] [data]");
}
@@ -226,9 +256,9 @@ public class Simulator {
throw new CommandFormatException("Illegal Address");
}
}
public void doFill(Command c) throws MemoryAccessException,
CommandFormatException {
CommandFormatException {
if (c.numArgs() != 3) {
throw new CommandFormatException("f [start] [end] [data]");
}
@@ -244,9 +274,11 @@ public class Simulator {
throw new CommandFormatException("Illegal Address");
}
}
public void doStep(Command c) throws IOException, MemoryAccessException,
CommandFormatException {
public void doStep(Command c) throws IOException,
MemoryAccessException,
FifoUnderrunException,
CommandFormatException {
try {
if (c.numArgs() > 0) {
cpu.setProgramCounter(stringToWord(c.getArg(1)));
@@ -257,16 +289,21 @@ public class Simulator {
throw new CommandFormatException("Illegal Address");
}
}
public void doGo(Command c) throws IOException, MemoryAccessException,
CommandFormatException {
public void doGo(Command c) throws IOException,
MemoryAccessException,
FifoUnderrunException,
CommandFormatException {
int readChar;
int stepCount = 0;
if (c.numArgs() > 2) {
throw new CommandFormatException("g [address] [steps]");
}
try {
int start = 0;
int steps = -1;
if (c.numArgs() > 0) {
start = stringToWord(c.getArg(0));
} else {
@@ -275,18 +312,56 @@ public class Simulator {
if (c.numArgs() == 2) {
steps = stringToWord(c.getArg(1));
}
// Make a gross assumption: Restarting the CPU clears
// the break flag and the IRQ disable flag.
cpu.clearBreakFlag();
cpu.clearIrqDisableFlag();
cpu.setProgramCounter(start);
outer:
while (!cpu.getBreakFlag() && (steps == -1 || steps-- > 0)) {
cpu.step();
if (trace) {
writeLine(cpu.toString());
}
// Wake up and scan keyboard every 500 steps
if (stepCount++ >= 500) {
// Reset step count
stepCount = 0;
//
// Do output if available.
//
while (acia.hasTxChar()) {
out.write(acia.txRead());
out.flush();
}
//
// Consume input if available.
//
// NOTE: On UNIX systems, System.in.available() returns 0
// until Enter is pressed. So to interrupt we must ALWAYS
// type "^E<enter>". Sucks hard. But such is life.
if (System.in.available() > 0) {
while ((readChar = in.read()) > -1) {
// Keep consuming unless ^E is found.
//
// TODO: This will probably lead to a lot of spurious keyboard
// entry. Gotta keep an eye on that.
//
if (readChar == 0x05) {
break outer;
} else {
// Buffer keyboard input into the simulated ACIA's
// read buffer.
acia.rxWrite(readChar);
}
}
}
}
}
if (!trace) {
writeLine(cpu.toString());
@@ -295,12 +370,12 @@ public class Simulator {
throw new CommandFormatException("Illegal Address");
}
}
public void doToggleTrace() throws IOException {
this.trace = !trace;
writeLine("Trace is now " + (trace ? "on" : "off"));
}
public void doReset() throws MemoryAccessException {
cpu.reset();
this.trace = false;
@@ -309,14 +384,15 @@ public class Simulator {
/**
* Main simulator routine.
*/
public static void main(String[] args) throws MemoryAccessException {
public static void main(String[] args) throws MemoryAccessException,
FifoUnderrunException {
try {
new Simulator().run();
} catch (MemoryRangeException ex) {
System.err.println("Error: " + ex.toString());
}
}
/*******************************************************************
* Private
*******************************************************************/
@@ -328,15 +404,15 @@ public class Simulator {
bus.write(address + i++, d);
}
}
private int stringToWord(String addrString) {
return Integer.parseInt(addrString, 16) & 0xffff;
}
private int stringToByte(String dataString) {
return Integer.parseInt(dataString, 16) & 0xff;
}
private void greeting() throws IOException {
writeLine("Welcome to the Symon 6502 Simulator. Type 'h' for help.");
}
@@ -364,7 +440,7 @@ public class Simulator {
private boolean shouldQuit(String line) {
return (line == null || "q".equals(line.toLowerCase()));
}
/**
* Command line tokenizer class. Given a command line, tokenize
* it and give easy access to the command and its arguments.
@@ -386,15 +462,15 @@ public class Simulator {
}
}
}
public String getCommand() {
return command;
}
public String[] getArgs() {
return args;
}
public String getArg(int argNum) {
if (argNum > args.length - 1) {
return null;
@@ -402,13 +478,13 @@ public class Simulator {
return args[argNum];
}
}
public int numArgs() {
return args.length;
}
public boolean hasArgs() {
return args.length > 0;
}
}
}
}