digitech-assembler

A simple "assembler" (actually outputs hex codes of the instructions in ASCII) for the minimal processor.

It supports R-, I- and J-Instructions.

Installation

Compile the assembler.c-File and run the executable. For example in Linux:

gcc assembler.c -o assembler

This program was not tested on windows, it should theorically work though using Visual Studio (or MSVC).

Usage

Run the compiled program with the path to the assembly file as it's first argument. You can optionally pass a filename for an output file. If you don't pass an output file, the program just writes to the terminal's output.

Example usage:

printing to terminal output

./assembler example.asm

writing to a new example.o file

./assembler example.asm example.o

How it works

It reads a file specified as a command line argument line by line. Then it tokenizes this line by splitting on spaces and commas. Using a map it then looks for the type of the instruction (R, I and J) and finally merges the arguments and the opcode into one instruction.

Configuration

The assembler is written in a way that you can easily add more instructions of your own type.

Modifying instruction size and adding an instruction

To add a bne instruction you could first modify the BITS_OPCODE to add room for the instruction.

Then you can modify the INSTRUCTIONS-Array and add the bne-instruction:

const Instruction INSTRUCTIONS[] = {
    {"add", 'r', 0x0},
    {"sub", 'r', 0x1},
    {"mul", 'r', 0x2},
    {"and", 'r', 0x3},
    {"or", 'r', 0x4},
    {"xor", 'r', 0x5},
    {"ldi", 'i', 0x6},
    {"jmp", 'j', 0x7},
    {"bne", "i", 0x8}
};

Modifying the output

In line 91, the instruction gets printed. Here you can modify the format to fit your needs.

You can for example print all instructions as decimal, separated by a space:

fprintf(output, "%d ", instruction);