AIS Router AI2524 - Manual (Page 125)

Chapter 7: Manually Loading System Images
August 1997 Page 7-25
2524UM
Flash Load Helper versus Dual Flash Bank
You might use Flash load helper rather than dual Flash bank for one of
these reasons:
z You want to download a new file into the same bank from which
the current system image is executing.
z You want to download a file that is larger than the size of a bank,
and hence want to switch to a single-bank mode.
z You have only one single-bank Flash SIMM installed. In this case,
Flash load helper is the best option for upgrading your software.
Refer to Use Flash Load Helper to Upgrade Software on Run-from
Flash Systems , for more information about working with Flash load
helper.
Understanding Relocatable Images
Because partitioning requires that run-from-Flash images be loaded
into different Flash memory banks at different physical addresses, im-
ages must be relocatable. A relocatable image is an image that contains
special relocation information that allows:
z The image to relocate itself whenever it is loaded into RAM fo
execution
z A download program with appropriate support to relocate the im
age before it is stored in Flash memory so the image can run in
place in Flash memory, regardless of where in Flash memory it is
stored
Run-from-Flash systems formerly ran nonrelocatable images that
needed to be stored in Flash memory at a specific address. As a result,
the image had to be stored as the first file in Flash memory. If th
image was stored at any other location in Flash memory, it could not
be executed in Flash memory, nor could the image be executed from
RAM. The relocatable image overcomes this limitation.
With Flash partitioning, the run-from-Flash images will not work un-
less they are loaded into the first device as the first file. This require
ment defeats the purpose of partitioning. However, relocatable images
can be loaded into any Flash partition (and not necessarily as the first
file within the partition) and executed in place.