AIS AI2524 user manual Flash Load Helper versus Dual Flash Bank, Understanding Relocatable Images

Chapter 7: Manually Loading System Images

Flash Load Helper versus Dual Flash Bank

You might use Flash load helper rather than dual Flash bank for one of these reasons:

zYou want to download a new file into the same bank from which the current system image is executing.

zYou want to download a file that is larger than the size of a bank, and hence want to switch to a single-bank mode.

zYou 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:

zThe image to relocate itself whenever it is loaded into RAM fo execution

zA 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.

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