Instructions for uploading new software to your GPSMAP® using Microsoft Windows 98 or later:

1. Download the appropriate self-extracting archive file onto your hard drive.
   
   
2. Unzip the files in the archive by running the downloaded executable file.
   
   
3. Connect your unit to a free serial port (Com 1, 2, 3, or 4) on your PC with a PC interface cable. Note: Not all Garmin products have PC interface cable accessories. For many fixed-mount marine applications, the user will need to build an appropriate cable to accomplish this.
   
   
4. Turn on your unit and ensure the Serial Data Format is set to "Garmin® Data Transfer" on comm port 1. You can find this setting in the Main Menu on the "Comm" tab's, "Port 1" tab.
   
   
5. Change to the directory in which you unzipped the files, (i.e., C:\Garmin), and run the update program, updater.exe. Select the appropriate serial port and click "OK" to begin the software upload. During the upload, the display will indicate "Software Loading...." The upload process should take 2-5 minutes to complete. When the upload is completed, the unit will reset itself and turn on normally.

The following are required to upload the software update into your Garmin GPS unit:

• IBM-compatible PC running Windows 98, Windows ME, Windows NT 4.0, or Windows 2000 operating systems and an available Com 1, 2, 3, or 4 port.
  
• PC Interface Cable for your GPS unit. The PC Interface Cable may be purchased through your local Garmin distributor or ordered direct from our Online Store. Note: The user will need to build an appropriate cable to interface with the GSD 20.