== About the CX7_PreloaderUpdate.bin file ==
The file contains the program which is stored in the internal flash of the CX7000, called Preloader.
The Preloader does the following:
1. Updates itself if there is a valid CX7_PreloaderUpdate.bin file in the root directory of the first partition of the SD card.
2. Initialize the external RAM.
3. Load TC/RTOS from the SD card into the external RAM and start it.
Newer versions can also start TC/RTOS from a second partition and activate a hardware watchdog. See changelog below.

In older images the CX7_PreloaderUpdate.bin was delivered directly in the root directory.
As the Preloader is always updated in the flash if it is different to the current version in the flash and there is no downgrade prevention,
this resulted in an update whenever an SD card with some old image was replaced by an SD card with some newer image,
and then again in a downgrade if a SD card with an old image was inserted again.

Every update/downgrade waits 2s for the power to stabilize and then takes about 8s. During these 8s a power outage results in a non functional CX7000.
This is also documented in the CX7000 manual under chapter 7.4.4 "Update image".
The 2s power stabilizing phase is signaled by the TwinCAT LED flashing between bright red and dim red.
The update phase is signaled by the TwinCAT LED being bright red.

There is no need to do a Preloader update or downgrade unless the newer features mentioned above are wanted/not wanted.

To prevent update failures, the file has been moved into the boot/preloader-update directory
and needs to be manually moved into the root directory of the SD card if an update/downgrade is wanted.
For older images, moving the CX7_PreloaderUpdate.bin file to a sub directory, renaming the file, or just deleting it, is recommend.

Preloader version history:
0.7.26979:             First release
2.0.240483:            Supports starting TC/RTOS from a second partition, should the first contain no valid filesystem or TC/RTOS.
newer than 2.0.240483: Starts a hardware watchdog if there is more than one valid partition with a supported filesystem.
                       Supports setting a priority to a partition in order to select from which partition TC/RTOS should be started.
                       Starts TC/RTOS from another partition, should a previous start have failed.
