Thread: Garmin eTREX 20 working as an eTREX 30

This link points to the same boot2.80.bin... [Only registered and activated users can see links. ]

I don't know what's 53 here...
Also I don't know exactly how many regions are there. It depends on the particular device. I only know that region number is encoded by one byte integer.
You can try dumping all the regions, but beware that some of them are huge (in particular, region number 48, containing the internal flash drive's filesystem).
Also you can try disassembling region handling functions. I haven't had time for this. Usually there is some table with region numbers and sizes inside every peace of code (fw_all.bin, boot.bin, bootloader), but some of the regions don't have fixed sizes and some of them are virtual with their contents stored inside files.
12 is a clearly virtual region, for example. When begin requested to flash region 12 (in pre-boot mode), the bootloader copies the received data into RAM and executes it.

As far as I know RAM doesn't have a region assigned to it. But it can be dumped with 0x04 USB command. GPSDaemon can do it, for example.