Motorola DSP56300 Toolkit

A toolkit for working with the Motorola (Freescale/NXP) DSP56300 family of digital signal processors, including an assembler, disassembler, and emulator.

Crates

Crate	Description
dsp56300-core	ISA constants, register indices, instruction decoder
dsp56300-asm	Assembler library/CLI
dsp56300-disasm	Disassembler library/CLI
dsp56300-emu	JIT emulator library/CLI
dsp56300-emu-ffi	C FFI layer; builds as a static library

Building

cargo build
cargo build --release
cargo test

Assembler

The dsp56300-asm crate provides a library and CLI for assembling DSP56300 source files.

# Assemble a file (default: 4-byte little-endian words)
dsp56300-asm program.s -o program.bin

# Native DSP byte order (3 bytes/word, big-endian)
dsp56300-asm program.s -o program.bin -f u24be

# Text output (a56-compatible LOD format)
dsp56300-asm program.s -f lod

# Print segment map to stderr
dsp56300-asm program.s -o program.bin -v

Output formats: u32le (default), u24be, u24le, lod.

As a library:

use dsp56300_asm::assemble;

let result = assemble("org p:$0\n  nop\n  jmp p:$0\n").unwrap();
assert_eq!(result.segments[0].words, vec![0x000000, 0x0C0000]);

Disassembler

The dsp56300-disasm crate provides a library and CLI for disassembling program memory into readable assembly.

# Disassemble a binary (default: 4-byte little-endian words)
dsp56300-disasm program.bin

# Native DSP byte order
dsp56300-disasm -f u24be program.bin

# Start at a specific address, limit output
dsp56300-disasm -s 0x100 -n 32 program.bin

Output is colorized when writing to a terminal (--color always|never|auto):

P:$000000  000000         nop
P:$000001  0C0042         jmp p:$0042
P:$000002  0A8580 001234  jclr #0,x:$ffffc5,p:$1234

As a library:

use dsp56300_disasm::disassemble;

let (text, len) = disassemble(0, 0x0C0042, 0);
assert_eq!(text, "jmp p:$0042");
assert_eq!(len, 1);

Emulator

The dsp56300-emu crate provides a core emulator with a JIT execution engine, built with the Cranelift compiler backend. A library and simple CLI for running an emulator are included.

use dsp56300_emu::core::{DspState, MemoryMap};
use dsp56300_emu::jit::JitEngine;

let mut pram = vec![0u32; 4096];
pram[0] = 0x0C0100; // JMP $100

let map = MemoryMap::from_pram_buffer(pram.as_mut_ptr(), pram.len() as u32);
let mut state = DspState::new(map);
let mut jit = JitEngine::new(pram.len());

state.run(&mut jit, 1000);
assert_eq!(state.pc, 0x100);

From C/C++

The dsp56300-emu-ffi crate exposes the same functionality through a C API.

Build the static library and include the header:

cargo build --release -p dsp56300-emu-ffi --no-default-features
# produces: target/release/libdsp56300_emu_ffi.a
# header:   crates/emu-ffi/include/dsp56300.h

Link with -ldsp56300_emu_ffi -ldl -lpthread -lm (Linux) or the platform equivalent. See crates/emu-ffi/include/dsp56300.h for the full API reference and crates/emu-ffi/examples/quickstart.c for a usage example.

Examples

The examples directory contains audio effects borrowed from the a56 assembler source tree. The scripts/dsp56300-run wrapper script assembles and runs them with live audio on Linux (requires cpp, ffmpeg, and aplay).

Example	Description
thru.a56	Pass-through (no processing)
caltone.a56	Sine wave calibration tone via table lookup
pink.a56	Pink noise generator
reverb.a56	Schroeder reverb
sixcomb.a56	Six-comb reverb
flange.a56	Flanging effect
chorus.a56	Chorus effect

Run any example with live audio using the runner script:

scripts/dsp56300-run examples/reverb.a56

References

• DSP56300 Family Manual, Rev 5 - referred to as "DSP56300FM" in source comments

Acknowledgements

The official Motorola DSP56300 assembler (asm56300), Version 6.3.15 was used for exhaustive roundtrip testing of the assembler and disassembler across the full instruction encoding space.

The DSP56300 emulator from xemu (originally based on DSP56001 emulation from ARAnyM, Hatari, and later adapted for DSP56300 emulation in XQEMU) was used for early differential testing for the JIT emitter.