Issue with Linker-Defined Objects __SEG_START_

[stephane_sst]

Hello,

For my application, I need to know addresses of memory segments defined at link time. I manage to do it for a segment call MY_ZEROPAGE, DEFAULT_ROM and for SSTACK.

But when I try to get the start address of the DEFAULT_RAM, I get the message :

WARNING L4024: No information available for segment 'DEFAULT_RAM'

I have carefully read the help on that topic, but don't find where I am wrong.

Here is My prm file (generated by ProcessorExpert) :

NAMESENDSECTIONS    Z_RAM                    =  READ_WRITE   0x0080 TO 0x00FF;    RAM                      =  READ_WRITE   0x0100 TO 0x017F;    MY_STACK                 =  READ_WRITE   0x0180 TO 0x027F;    ROM                      =  READ_ONLY    0xE000 TO 0xFD9F FILL 0x82;    CONST_DATA               =  READ_ONLY    0xFDA0 TO 0xFDB9 FILL 0x82;ENDPLACEMENT    CONST_ROM_DATA                      INTO  CONST_DATA; /* Added manually */    DEFAULT_ROM, ROM_VAR, STRINGS       INTO  ROM;    DEFAULT_RAM                         INTO  RAM;    _DATA_ZEROPAGE,                     /* zero page variables */    MY_ZEROPAGE                         INTO  Z_RAM;    SSTACK                              INTO  MY_STACK;   /* Added manually */ENDINIT _EntryPoint                       /* The entry point of the application. This function is generated into the CPU module. */STACKTOP  0x027F                       /* Top address of the system stack. Value can be changed on the "Build options" tab */

and below, the source code :

extern char __SEG_START_MY_ZEROPAGE[];extern char __SEG_END_SSTACK[];extern char __SEG_START_DEFAULT_RAM[];void Function(void){  unsigned char * pucZRam;  /* Step 1 : write all zeros */  for (pucZRam = (unsigned char *) __SEG_START_MY_ZEROPAGE;       pucZRam < (unsigned char *) __SEG_START_DEFAULT_RAM;       pucZRam++)  {    *pucZRam = 0;  }  }

The map file confirms that ther is an issue with DEFAULT_RAM, since address value is 0 :

...

- LABELS:
     __SEG_START_MY_ZEROPAGE                     80       0       0       1               
     __SEG_START_DEFAULT_RAM                      0       0       0       1 
...

Help is welcome.

Thanks

[CrasyCat]

Hello

  In your application I assume you do not have anything allocated in section DEFAULT_RAM.

  So the section does not exist and you cannot retrieve its start address or size.

CrasyCat

[stephane_sst]

Ok, I think that I understand what you mean.

Actually, I don't have explicitelly allocated any variables in DEFAULT_RAM segment.

In my current PRM file, the DEFAULT_RAM segment belongs to the RAM section, from 0x100 to 0x17F.

Thanks to the map file, I see that I have some variables placed by default in this memory area. But, they don't belong to DEFAULT_RAM, if I am right.

- VARIABLES:     uiCurrentStackPointer                      100       2       2       2   .bss             bTestRamPassed                             107       1       1       2   .common  

How can I explicitely allocate variables into the DEFAULT_RAM sections?

I tried to use the pragma directive, but without success :

#pragma DATA_SEG DEFAULT

I am able to get the start address of bss section, thank to __SEG_START___DOT__bss.

But I am not sure if this is the right way to get the start and and addresses of DEFAULT_RAM.

[CrasyCat · Accepted solution]

Hello

  Per default the compiler will use following predefined section names to allocate variables:

      .data :     Contains the initialized global variables (also called DEFAULT_RAM).
                        e.g. int a = 1, b= 2;
      .bss :     Contains the static un-initialized global variables.
                        e.g. static int c, d ;
      .common : Contains the un-initialized global variables.
                        e.g. int e, f;

So if you only have un-initialized global variables in your application DEFAULT_RAM section will not be used. You can then retrieve start address for RAM using _SEG_START___DOT__bss.

If you really want to allocate a variable in DEFAULT_RAM section, do the following:

#pragma DATA_SEG .data#pragma DATA_SEG DEFAULTint var @".data";

CrasyCat

[stephane_sst]

Thank you for the explanations, things get clear.

This topic is closed for me.