LS-8: 8-Bit Computer Emulator V2.0

In this project, we attempted to implement a turing complete emulator of an 8-bit CPU in Python, the pedagogical purpose of the assignment being to understand more deeply how a programming language works. Through the creation of virtual RAM, the use of binary and hexadecimal integers, as well as subroutine CALL and RETURN functions, I definitely achieved a much deeper understanding of computer processing, as well as became more comfortable working with different number bases.

Since achieving the minimum viable product, I have implemented my own changes to make the CPU feel more fun and functional.

Important Files

• LS-8 CPU (Main Program!)
• LS-8 Specifications
• LS-8 FAQ
• LS-8 Programs (Proof of Functionality)
• ASM to LS-8 Compiler

Running Programs on the LS-8

The LS-8 is a console-based computer. When running the loader file, you must make sure you're in the proper directory in order to ensure that programs can be correctly loaded.

1. Move into the ./ls8 directory (necessary to read in programs!):

   cd ls8

2. Run the ls8.py file:

   python ls8.py

Now your CPU is up and running! When prompted, enter the name of a valid LS-8 program in the programs directory. Errors are handled for nonexistent names, and should not negatively impact the user experience.

If no extension is specified, .ls8 is automatically appended to the filename you enter. For instance, entering

>> mult

will attempt to load the file

>> mult.ls8

See below for a list of reserved keywords that are the exception to this rule, and should not be used as program names.

Reserved Keywords

• exit will cause the LS-8 to exit (shutdown)
• list will print a list of the programs in the programs directory
• help will print these keywords during runtime

Tip: The esc key will flag the program loop to exit, ending any loops. This is particulary useful for the given interrupts.ls8 and keyboard.ls8 example programs

Notes About .ls8 Syntax

.ls8 files need to follow strict guidelines to run, as the CPU loader is not very "smart".

• Instructions must be written in 8-bit binary code.
• Only one instruction per line.
• Instructions may be followed by comments, which the loader ignores.
• Blank lines are allowed, and are ignored by the loader.
• Comments may be alone on a line, and are ignored by the loader.
• Comments must begin with # , or the loader will throw an error and stop program execution.

V2 Checklist

Implementation Complete

On top of the desired features listed in the below checklist, this version also includes UI improvements and improvements to code readability and modularity.

• Put the load() method call inside the run() method, and create a system wherein users can load functions on the fly, and load another function when the first one is done executing
• Move file input processing from ls8.py into the CPU load() method
• Refactor ram functions
• Bonus: remove excess print statements and simplify run() loop

V3 Feature Wish List

These goals will be fairly difficult to implement, and will require the refactoring of any of the example program files that use the RET or CALL functions. They will also cause the compiler and the cpu.run() method to require tweaks, and as such may not be appropriate for the desired simplicity of an 8-bit CPU (though they are still very possible).

• Add parameters to subroutine CALLs
• Add return values to RET

Conclusion

That's all you need to know to begin programming with the LS-8! If you found this program particularly interesting or would like to know more, feel free to reach out to me via LinkedIn.

Thanks for reading!