Seth Morabito
795ccfde5d
Bug Fixes: - Fixed several bugs in the CPU that caused processor status flags to be set incorrectly. Instructions affected were: STA, STX, STY, CMP, CPX, CPY, BIT. - Made some internal-use-only methods on the CPU class private. - Fixed incorrect disassembly of (Indirect,X) and (Indirect),Y instructions. Although this didn't affect behavior, it certainly caused me some confusion in debugging. - Added missing "BCS" instruction to instruction table. Enhancements: - Now includes a full version of Lee Davison's Enhanced 6502 BASIC bundled as source code and a ROM image. Get that REAL COMPUTER EXPERIENCE!(tm) - If a file named "rom.bin" exists in the same directory where the simulator is executed, it will be loaded at addresses $d000-$ffff. - Gave the CPU an idle loop to make simulated timing a little more realistic (but this is still an area needing major improvement) - Changed the CPU's toString() method to give better debugging output. - Added a small typeahead buffer to the Console. - Better exception messaging. Misc: - Bumped version to 0.5, updated README.
122 lines
3.2 KiB
Markdown
122 lines
3.2 KiB
Markdown
SYMON - A 6502 System Simulator
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===============================
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**NOTE: THIS IS BETA QUALITY SOFTWARE UNDER ACTIVE DEVELOPMENT. Feedback is
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welcome!**
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**Version:** 0.5
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**Last Updated:** 21 October, 2012
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Copyright (c) 2008-2012 Seth J. Morabito <web@loomcom.com>
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See the file COPYING for license.
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## 1.0 About
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Symon is a general purpose simulator for systems based on the NMOS
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Mostek 6502 microprocessor and compatibles. Symon is implemented in
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Java. Its core goals are accuracy, ease of development, clear
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documentation, and extensive test suites for validating correctness.
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The initial goal is to simulate a system with an NMOS 6502 or CMOS
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65C02 central processor; one or more 6522 VIAs; and one or more 6551
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ACIAs. More functionality may be considered as time goes on.
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## 2.0 Requirements
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- Java 1.5 or higher
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- Maven 2.0.x or higher (for building from source)
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- JUnit 4 or higher (for testing)
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## 3.0 Usage
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### 3.1 Building
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To build Symon with Apache Maven, just type:
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$ mvn package
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Maven will build Symon, run unit tests, and produce a jar file in the
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'target' directory containing the compiled simulator.
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Symon is meant to be invoked directly from the jar file. To run with
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Java 1.5 or greater, just type:
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$ java -jar symon-0.3-jar-with-dependencies.jar
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When Symon is running, you should be presented with a simple graphical
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interface.
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### 3.2 Loading A Program
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Programs in the form of raw binary object files can be loaded directly
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into memory with the "Load" button.
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Right now, all programs are loaded starting at addres $0300. After
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loading, the simulated CPU's reset vector is loaded with the values
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$00, $03, and the CPU is reset.
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There are two very simple sample program in the "samples" directory,
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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.
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The sample directory also contains a ROM image of Lee Davison's
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Ehanced 6502 BASIC. For instructions on loading the rom, please see
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the README file in that directory.
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### 3.3 ROM files
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Any 12KB file named 'rom.bin' that exists in the same directory where
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Symon is launched will be loaded at address $d000. If the file is
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larger than 12KB, loading will fail. This functionality will be
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improved in a future release!
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### 3.4 Running
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After loading a program or ROM image, clicking "Run" will start the simulator
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running at address $0300.
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## 4.0 To Do
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- Better debugging tools from the UI, including memory inspection,
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disassembly, breakpoints, and execution tracing.
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- Better ROM loading (and re-loading)
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- More accurate timing.
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- Interrupt handling!
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- UI needs a ton more polish.
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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
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by start address and end address. They should both use start/end
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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
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debugging.
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## 5.0 Licensing
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Symon is free software. It is distributed under the MIT License.
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Please see the file 'COPYING' for full details of the license.
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