1. Boot code is stored in raw flash (no file system) and directly accessed from bootloader
2. Boot code is stored on a Reliance formatted flash volume

Option 1: Raw flash
If the boot image is being stored in RAW flash outside the file system, then the only way to be able to ensure that you got an update without damaging the original would be to reserve extra RAW space such that you could simultaneously have two boot images. The bootloader now needs to be able to switch between them and/or locate both of them The process of updating the boot image to a new location would include erasing the old image after updating the new, and having some sort of checksum to ensure the image was intact in case both were still there.

In this case, there would be no really good way to protect the update of the file to that exact same location without compromising the boot image itself. Many customers still use this way to store their boot images, but of course this means that they can’t take advantage of disabling transactions, atomically updating the boot image, and then doing a single transaction to commit all (or none) of the changes.

Option 2: Reliance
In this case, customer would not have a bootloader that checked a physical location for a boot image – they would have a bootloader that opened a file in the Reliance file system at boot time instead, if they were using a file system. Datalight Reliance comes with an utility called “Datalight Loader” which includes a lightweight Reliance reader. This utility integrates seamlessly in your bootloader code and allows the bootloader to mount and read Reliance partitions. Since the bootloader is capable of “reading” a Reliance disk, it doesn’t care where in the file system Reliance stores the file – it just opens the file, and loads it.

In this mode, while updating the boot image, the update utility disables all transactions and initiates the boot image update. Reliance never overwrites live data and hence this new boot code is written to a free-area of the flash. Once the entire boot image code is written, the bootloader calls for a manual transaction event, in which we update the metaroots to point to the new boot code area as the committed area. Old boot code area is now marked as free and can be used for future operations.

If power loss occurs during this replacement process, the device still boots back using the previous boot image, which was never modified

Given the popularity of VxWorks amongst our customer based, we have prospective VxWorks customers ask us how our products are installed and configured on that platform. This short blog post will try and answer these questions. If you have more questions, please leave a comment and we will get back to you.

Q: How does a customer install Datalight VxWorks products
We ship our products with an image of what would be put on a CD, so customers can extract our installation ZIP files into a temporary directory, and run SETUP.  This will install our product into a directory that they tell us (usually c:\dl\flashfx or c:\dl\reliance) and will add our CDF (WorkBench catalog files) in the appropriate place in the Workbench tree.
Q: How do they configure it?  If it’s a menu structure (like Tornado’s Project) where is the menu, what are the options, and what are their effect?

In Workbench and Tornado, FlashFX Pro shows up in the Catalog right next to the TFFS flash driver, and Reliance shows up right next to dosFS.  Our manuals for VxWorks provide step-by-step guidance on how our products can be configured using the VxWorks development IDEs
Q: What effort is involved in using the Datalight Reliance or FlashFX Pro file system on VxWorks?
Developers use the standard file system APIs of VxWorks (file open, file close, etc) like they would if dosFS or another file system and don’t need to know anything specific about the API of Reliance.  Same with FlashFX Pro – once we’re working in the environment, we’re a “disk”, and the people writing applications don’t need to know any special APIs.