HwSim6809 Hardware Simulator for MC6809 Systems

Jan. 10, 2013 - This project is the experimental development of a hardware simulator for MC6809 based systems. This project is also courseware, being written for student use in a computer engineering course that I teach. This project is first inspired by the perceived need for a 6809 system simulator capable of executing a stub or "talker" program in a target system, and communicates through a port, with a remote debugger user interface.

Operating systems such as Linux and Windows each have the means to create a pair of serial ports that route to each each other. Such applications are referred to as a "null-modem emulator," or "serial port redirector," or "relay for bidirectional data transfer." For Linux and Windows, socat and com0com each serve as examples.

It is hoped that such a simulator, when used with a debugger user interface designed for use with actual hardware, will provide an environment that is more realistic, more like "real" hardware, than having a simulator integrated into the debugger. It is not a goal of this project to provide a bus level simulation, rather for that, consider using a VHDL description and simator which may be more appropriate.

I am coding with C and Lua, in an attempt to strike a balance between flexibilty and performance. Having the simulator core in C provides performance where it counts most. The C code is compiled to a library, whereby the library functions are called from Lua. On Linux such a library is called a ".so" or "shared object" and on Windows its called a ".dll" or a "dynamic-link library."

For flexibilty I chose to also use a scripting language. Among interpreted languages, Lua is reported to be very fast. Lua will be used for the higher level coding and to provide a means to "attach" modules that each model a peripheral device.

For portability, the C code will be as generic as possible, so that the simulator can easily be built for various host systems. I will rely on Lua's cross-platform libraries to provide some independence from the operating system in dealing with such things as a serial communication port.

In writing the code I'm finding that I like also being able to "run the simulator," using a command line line environment. Perhaps some day a graphical user interface can be incorporated. Having even a rudimentary simulator interface may be a benefit to my students.

HwSim6809 Hardare Simulator for MC6809 Systems