The "Serialdown" or "USBdown" mode is selected depending on the recovery strategy.
This is the most sensitive part of the discussion. The official GXDownloader Boot v1032 is proprietary software owned by Mitsubishi Electric Corporation. gxdownloader boot v1032 link
The user selects the correct COM Port and chooses the specific Chip Type (e.g., GX6605S) within the software interface. The "Serialdown" or "USBdown" mode is selected depending
How to Recover Your Satellite Receiver Using GXDownloader Boot V1.032 gxdownloader boot v1032 link
Because this is niche technical software, official "brand" websites rarely host it. It is most commonly found on satellite enthusiast forums and technical file-sharing communities.
Known for being a stable choice for GX-based boards compared to generic loaders.