c1caf8c6b4
This change introduces simulated baud rates in the ACIA. Baud rate is controlled just as in the real 6551, by writing to the ACIA's control register. Baud rates between 50 and 19,200 baud are selectable. A baud rate of 0 has special meaning, and turns off all simulated baud rate delays (on a real 6551, this means to use an external clock instead of the internal baud rate generator) A busy-wait loop between steps in the simulator control program has also been added. This uses the high-resolution 'System.nanoTime()' call to wait a specific number of nanoseconds before continuing. Symon now waits at least 1uS between clock cycles, trying to approach a real 1MHz 6502 in performance. It is far from perfect, but it's better than it was. Also refactored the status panel to use a BoxLayout, and DRY-up some of the code.
SYMON - A 6502 System Simulator
NOTE: THIS IS ALPHA QUALITY SOFTWARE UNDER ACTIVE DEVELOPMENT. IT IS NOT YET FULLY FUNCTIONAL. IT MAY BE USEFUL, BUT IT IS NOT YET INTENDED TO BE USED BY ANYONE BUT DEVELOPERS. Feedback is welcome!
Version: 0.3 Last Updated: 14 October, 2012
Copyright (c) 2008-2012 Seth J. Morabito <web@loomcom.com>
See the file COPYING for license.
1.0 About
Symon is a general purpose simulator for systems based on the NMOS Mostek 6502 microprocessor and compatibles. Symon is implemented in Java. Its core goals are accuracy, ease of development, clear documentation, and extensive test suites for validating correctness.
The initial goal is to simulate a system with an NMOS 6502 or CMOS 65C02 central processor; one or more 6522 VIAs; and one or more 6551 ACIAs. More functionality may be considered as time goes on.
2.0 Requirements
- Java 1.5 or higher
- Maven 2.0.x or higher (for building from source)
- JUnit 4 or higher (for testing)
3.0 Usage
3.1 Building
To build Symon with Apache Maven, just type:
$ mvn package
Maven will build Symon, run unit tests, and produce a jar file in the 'target' directory containing the compiled simulator.
Symon is meant to be invoked directly from the jar file. To run with Java 1.5 or greater, just type:
$ java -jar symon-0.3-jar-with-dependencies.jar
When Symon is running, you should be presented with a simple graphical interface.
3.2 Loading A Program
Programs in the form of raw binary object files can be loaded directly into memory with the "Load" button.
Right now, all programs are loaded starting at addres $0300. After loading, the simulated CPU's reset vector is loaded with the values $00, $03, and the CPU is reset.
There are two very simple sample program in the "samples" directory, for testing.
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'echo.prg' will echo back anything typed at the console.
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'hello.prg' will continuously print "Hello, 6502 World!" to the console.
3.3 Running
After loading a program, clicking "Run" will start the simulator running at address $0300.
4.0 To Do
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Accurate timing (all simulated instructions currently take only one step to execute)
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Interrupt handling!
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UI needs a ton more polish.
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Add a simple menu interface for common tasks.
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More extensive testing.
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Clean up JavaDoc.
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Busses are defined by start address and length. Devices are defined by start address and end address. They should both use start/end address.
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Implement CMOS 65C02 instructions and NMOS / CMOS mode flag.
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Allow a flag to disable breaking to monitor on BRK.
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Allow displaying ACIA status and dumping ACIA buffers, for debugging.
5.0 Licensing
Symon is free software. It is distributed under the MIT License. Please see the file 'COPYING' for full details of the license.