Echelon LonTal Stack - Manual (Page 216)

204 Appendix F: Appendix F
Downloading a LonTalk Stack Application Over
the Network
application download utility to delay additional updates until the application is
ready to receive the data.
After the transfer is complete and all data has been written to non-volatile
memory, the application must prepare the image so that the boot loader can
reboot the embedded processor from the new image. This preparation must be
defined so that a device or processor reset at any point will result in a functioning
LonTalk Stack device. For example, the reset could always cause a boot from the
old application image, or from the new application image, or from some
temporary boot application that can complete the transition (possibly with user
intervention).
Another issue to consider is whether the entire image will be loaded or only a
partial image. It is far simpler, and more flexible, if the entire image, including
the LonTalk host stack and the operating system can be replaced. However,
loading the entire image can take several minutes (for example, loading an
application such as the simple example application could require 10 minutes or
longer). Loading only the application portion of the image is possible if you
structure your application very carefully. For example, you might need to
provide patchable linkage stubs that allow your loaded application image to
interact with the pre-loaded LonTalk host stack library and operating system.