minisrc-assembler

Customizable RISC Assembler by describing a language in yaml or json. Originally made this for ELEC374 Digital Systems Engineering

Note: One feature that could be missing that is useful is custom ways to interpret values. At the moment you technically could do whatever you want in things like branch instructions through the opcode and extra formats, however the configurations for that would be very clunky. There might be a way to solve this similar to how conditions are done, however it is difficult for me to describe.

ALSO: If you are using this for ELEC374 and notice any bugs/incorrect instructions, please let me know so that I can get them fixed. I think that everything should be working but I have yet to make sure.

Usage

Flag -x (--hex) makes the numbers output in hexadecimal to the file in utf-8.
-b makes it output binary in utf-8.
No flag (default) will cause it to write to the file as binary (no encoding)

python3 minisrc-asm.py -s <ASM_INPUT_FILE> -o <OUTPUT_FILE>

Note: If no output file name is specified, output will only be printed to terminal

Single Instruction

python3 minisrc-asm.py -l "ldi r4, 0x87(r3)"

Example

-v will cause the program to print out each instruction as and its converted format in hex

python3 minisrc-asm.py -v -s tests/instructions.s -o tests/instructions.hex

Instruction set Configuration

The configuration for can be (fully?) customized for any different instructions, opcodes, and binary formats.

To interpret a value in a field in a certain way, the field must have a certain string inside of it. The strings are:

• opcode: raw value
• R: as a register (The value of the register in the machine instruction is directly taken from the assembly instruction)
• imm: as an immediate value

An example of a configuration is:

---
name: example
word_size: 32
textformats: # the fields must be in the order that they would be in assembly
    - name: one_reg
      fields: [opcode, Ra]
    - name: misc
      fields: [opcode]
conditions:
    - name: branch
      value: 2 # value that will be placed in spot of condition for instruction with the above name
formats: # format for how values will be placed in each word
    - name: M
      fields:  # msb and lsb are the range for where the value will be
        - { name: opcode, msb: 31, lsb: 28 }
    - name: B
      fields: 
        - { name: opcode, msb: 31, lsb: 28 }
        - { name: condition, msb: 19, lsb: 16 }
        - { name: Ra, msb: 3, lsb: 0 } 
instructions:  # list of instructions in the instruction sete
  - { name: nop, opcode: 13, format: M, textformat: misc }
  - { name: branch, opcode: 4, format: B, textformat: one_reg }

Running with this configurations gives

python3 minisrc-asm.py -c examples/example.yaml --use-yaml -l "branch r5"
branch r5            :  0x40020005
python3 minisrc-asm.py -c examples/example.yaml --use-yaml -l "nop"
nop                  :  0xd0000000

This can also be done in json although it is a little longer:

{
    "name": "example",
    "word_size": "32",
    "textformats": [
        {
            "name": "one_reg",
            "fields": [ "opcode", "Ra" ]
        },
        {
            "name": "misc",
            "fields": [ "opcode" ]
        }
    ],
    "conditions": {
        [
            {
                "name": "branch",
                "value": 2
            }
        ]
    },
    "formats": [
        {
            "name": "M",
            "fields": [
                {
                    "name": "opcode",
                    "msb": 31,
                    "lsb": 28,
                }
            ]
        },
        {
            "name": "B",
            "fields": [
                {
                    "name": "opcode",
                    "msb": 31,
                    "lsb": 28,
                },
                {
                    "name": "condition",
                    "msb": 19,
                    "lsb": 16,
                },
                {
                    "name": "Ra",
                    "msb": 3,
                    "lsb": 0
                }
            ]
        },
    ],
    "instruction": [
        {
            "name": "nop",
            "opcode": 13,
            "format": "M"
        },
        {
            "name": branch,
            "opcode": 4,
            "format": "B"
        }
    ]
}