What is startup data structure for S12ZVM and How it gets intialised ?

[ameykhatavkar]

Hi,

While going to the start up code I come across the startupData structure.

*********************************************************************************************

STARTUP SECTION

---------------------------------------------------------------------------------------------

Entry point: 0xFE004F (_EntryPoint)

_startupData is allocated at 0xFE00A2 and uses 20 Bytes

extern struct _tagStartup {

  unsigned nofZeroOut     1

  _Range   pZeroOut       0x1200     62

  _Copy    *toCopyDownBeg 0xFE052A

  int      nofInitBodies  0

  _Cpp     *initBodies    0xFE00BD

  int      nofFiniBodies  0

  _Cpp     *finiBodies    0xFE00BD

} _startupData;

I understood the code, but I would like to know that, how it gets initialized?

Who is responsible for the same?

And is it always located at address 0xFE00A2 ?

Also Is EntryPoint address (0xFE004F is always same?

Regards,

Amey

[RadekS]

Hi Amey,

Please check start12z.c and start12z.h file in your project/Project Settings/Startup_Code.

This structure is used for initialize RAM prior start main() routine. The default bare metal project execute _Startup() function after reset. This _Startup() function will erase and initialize RAM.

Note: If you use ProcessorExpert, the reset vector points to _EntryPoint() instead of _Startup() .

Startup code is placed by linker, therefore location of this code could vary according linker settings and your project size.  

Note: prm linker file is in your project/Project Settings/Linker_Files.

You could try for example specifying some part of RAM and filling them by some pattern. For example:

RAM3          = READ_WRITE  0x003000 TO 0x003FFF FILL 0x33;

In that case startup code will initialize this part of RAM prior enter into main() function.

The similar way you could also copy some code from flash into RAM (RELOCATE_TO).

See "c:\Freescale\CW MCU v10.6\MCU\Help\PDF\MCU_Build_Tools_Utilities.pdf" document for more details.

I hope it helps you.

Have a great day,
RadekS

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