Introduction
Table of contents
Overview
The SidecarTridge ROM Emulator is a developer-oriented module that emulates parallel ROM devices (e.g., 27C/28C families) at the signal level, letting you load, select, and switch between multiple binary images without physically swapping chips. It’s the same core technology used in the SidecarTridge TOS product to boot different Atari ST TOS versions and custom ROMs, presented here as a general-purpose building block you can integrate into your own projects.
The ROM Emulator combines solid hardware (RP2350 + PIO) with a simple host workflow: the on-board flash is exposed as a USB mass-storage volume, you copy images to it, and then select which image is active. Tools and firmware features include FAT12 handling and self-hosted image management (yes, it’s possible to upload images directly from the computer running the emulator).
What you can do with it
- Boot different firmware/OS ROMs on a target system for development, diagnostics, or preservation.
- Keep a library of ROM images (up to 64 within 16 MB) and switch without opening the machine.
- Script image selection and management from the self-hosted environment, or the host API.
- Reuse the proven approach from the TOS product to run official and custom ROMs on real hardware for different computer systems.
Where it fits in the SidecarTridge ecosystem
The ROM Emulator exists to bring the same benefits proven in the SidecarTridge TOS Emulator to other computers and embedded targets—without being tied to Atari ST specifics. In practice, it gives you multi-image ROM libraries, hot/image switching without chip swaps, and host-driven, scriptable workflows for build/test—now applicable to any platform that expects a parallel ROM/EPROM/Flash device.
How it works (high level)
At runtime, RP2350 PIO state machines present address, data, and control timings compatible with standard ROM/EEPROM/Flash parts (CS#, OE# behavior), while the active image is fetched from on-board flash. The device enumerates as a FAT12 USB mass-storage volume for easy image management; self-contained tools can also upload and switch images programmatically.
Who is this for?
- Developers & hardware hackers who need repeatable ROM testing without burning chips.
- Retrocomputing enthusiasts who want to run official or community ROMs on original hardware.
- Integrators/OEMs who need a compact, embeddable ROM solution in custom projects.
Capabilities and limits (at a glance)
- Supports common parallel ROM pinouts in 8- or 16-bit data widths and sizes from 4 KB to 512 KB per image (within the device’s 16 MB storage).
- Stores up to 64 images and can switch the active image without a power-cycle (by host command or mapped triggers, depending on firmware setup).
- Supports bus speed from 1 MHz to 24 MHz (depending on firmware configuration and target hardware).
- Designed as a module to integrate; it is not a standalone consumer product.
Prerequisites & related docs
If you’re evaluating this module because you’ve seen the TOS product, the TOS documentation offers helpful patterns for installation, operation, and recovery flows that translate well to other targets:
- https://docs.sidecartridge.com/sidecartridge-tos/