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STR71x MEMORY MAPPING AND DEVELOPMENT TOOLSET

1 USING SCATTER FILES FOR IMAGE ORGANIZATION IN MEMORY

This paragraph describes how to place and organize the data and code in memory. It focuses

on the use of the scatter-loading file for the RealView toolset.

An image is made up of regions and output sections. Every region in the image can have a dif-

ferent load and execution address. The scatter-loading mechanism enables you to specify the

memory map of an image to armlink. For more information on the scatter file, load and execu-

tion regions, please refer to ’ARM Linker and Utilities Guide’.

Following reset, the processor starts to fetch instructions from the reset vector at the address

0x00000000. This instruction should transfer control to the initialization code. The entry point

must lie within an execution region that must be a root region. For this reason, the vector and

initialization routines must always be present at the address 0x00000000.

Different types of memory are present in our system so different mappings can be used de-

pending on the boot mechanism. For further information on boot modes, refer to the STR71

datasheet.

The following table explains the use of the different scatter loading files.

Table 1. Scatter file use

1.1 BOOTING FROM RAM

On power-up the RAM is located at address 0x00000000. The first section is a root region

made up of the vector and initialization routines.

The contents and the organization of the scatter loading description file are shown below.

RAM_MODE 0x20000000 0x10000 ; Load region starts at the real RAM address

{

RAM 0x20000000

; Startup exec region address is the same as the

{

; load address (root region)

71x_vect.o (Vect, +First); - Section containing the entry point

71x_init.o (Init)

; - Section containing the init routines

* (+RO)

; - The code and the read only data are placed

;

after the init routine

* (+RW)

; - The read/write data (variables)

* (+ZI)

; - The zero initialized region is placed after

}

;

the read/write data

}

Scatter File

Boot mode

71x_armr

Booting from RAM

71x_arme

Booting from External Memory

71x_armf

Booting from Embedded Flash

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