MU0 - Simplified Processor Emulator

This is a simple emulator for the MU0 processor, written in Python 3. It has two registers, the program counter PC and the accumulator ACC, and it understands a language with the following instruction set:

Opcode	Instruction	Effect description
0000	LOAD X	ACC = memory[X]
0001	STORE X	memory[X] = ACC
0010	ADD X	ACC = ACC + memory[X]
0011	SUB X	ACC = ACC - memory[X]
0100	JUMP X	pc = X
0101	JGE X	if ACC>=0 pc = X
0110	JNE X	if ACC!=0 pc = X
0111	STOP	stop

The extra assembly pseudoinstruction INI X Y is available, in order to load values into the memory. Values range is from -2¹¹ to 2¹¹ - 1, encoded in two's complement. All the values are statically loaded before the program start, regardless of their position in the code. All values and immediates must be expressed in hexadecimal form, preceded by the 0x prefix. The address space is 2¹² bit, so eventual instructions containing a bigger address (more than 3 hex digits, including leading zeroes) are refused as invalid.

Comments are introduced by semicolon and may follow an instruction or may occupy an empty line. Blank lines (empty, or containing spaces only) are allowed.

Note that the address in the JUMP instruction is relative to the number of the instruction (zero-based and ignoring blank lines, comment lines and INI pseudoinstruction lines) and not to the mere line number in the source file

Run

The program has been implemented both into a simple terminal script and into a tkinter graphic application.

To start the graphic application (needs the Tk support, it should be bundled with most python installations), run:

python mu0_graphic.py

With the graphic application you can write your code or open an existing source file, save your program or run it.

If you do not have Tk support, you can use the alternate script. To run a program in the console, without interruptions, the emulator should be invoked as:

python mu0.py source_filename

To run a program step by step, pausing and showing the system status after each instruction, add the -s option:

python mu0.py -s source_filename

Here source_filename is the name of a source file written according to the rules in the section above. A sample source file (sample_program.asm) is provided with the project.

License

The project is licensed under GPL 3. See LICENSE file for the full license.