This is an assembler that takes custom, user-defined instruction sets and uses them to assemble source files.
This can be useful if you'd like to test out a new virtual machine's bytecode, or even if you're eager to write programs for that new processor architecture you just implemented in FPGA!

📱 Try it right now on your browser!

📖 Check out the User Guide for instructions!

🕹 Check out an example project which targets the NES!

💻 Install the VSCode syntax highlight extension!

❤️ A big thank you to my supporters!

📖 Check out instructions for migration from older versions to v0.11!

You can install directly from crates.io by running cargo install customasm. Then the customasm application should automatically become available in your command-line environment.

You can also download pre-built executables from the Releases section.

You can compile from source yourself by first cloning the repository and then simply running cargo build. There's also a battery of tests available at cargo test.

Given the following file:

#ruledef
{
    load r1, {value} => 0x11 @ value`8
    load r2, {value} => 0x12 @ value`8
    load r3, {value} => 0x13 @ value`8
    add  r1, r2      => 0x21
    sub  r3, {value} => 0x33 @ value`8
    jnz  {address}   => 0x40 @ address`16
    ret              => 0x50
}

multiply3x4:
    load r1, 0
    load r2, 3
    load r3, 4
    
    .loop:
        add r1, r2
        sub r3, 1
        jnz .loop
    
    ret

...the assembler will use the #ruledef directive to convert the instructions into binary code:

 outp | addr | data

  0:0 |    0 |          ; multiply3x4:
  0:0 |    0 | 11 00    ; load r1, 0
  2:0 |    2 | 12 03    ; load r2, 3
  4:0 |    4 | 13 04    ; load r3, 4
  6:0 |    6 |          ; .loop:
  6:0 |    6 | 21       ; add r1, r2
  7:0 |    7 | 33 01    ; sub r3, 1
  9:0 |    9 | 40 00 06 ; jnz .loop
  c:0 |    c | 50       ; ret

Usage: customasm [options] <asm-file-1> ... <asm-file-N>

Options:
    -f, --format FORMAT The format of the output file. Possible formats:
                        binary, annotated, annotatedbin, binstr, hexstr,
                        bindump, hexdump, mif, intelhex, deccomma, hexcomma,
                        decc, hexc, logisim8, logisim16
    -o, --output [FILE] The name of the output file.
    -s, --symbol [FILE] The name of the output symbol file.
    -t, --iter [NUM]    The max number of passes the assembler will attempt
                        (default: 10).
    -p, --print         Print output to stdout instead of writing to a file.
    -q, --quiet         Suppress progress reports.
    -v, --version       Display version information.
    -h, --help          Display this information.