S12 / MagniV Microcontrollers中的主题 Re: Strings going to SRAM

Strings going to SRAM

manishsangram — Thu, 02 Jun 2016 18:48:08 GMT

Hi,

We are using S12ZVMC128 MCU.

All string constants declared in the application code get assigned to SRAM by the compiler. As per what we have read constant strings should be in Flash RAM.

What settings have to be changed / declaration made to avoid this ?

Re: Strings going to SRAM

iggi — Fri, 03 Jun 2016 09:31:46 GMT

Hi,

The most probably you didn't put const in front of the string defined:

const char mystring[] = "Hello";

With the const, constant string can be allocated to Flash, otherwise it will be distributed to RAM.

Also, you can use us #pragma declaration define a segment (constant, data, code) and still 'const' is necessary

Syntax: #pragma CONST_SEG <name>|DEFAULT

This segment must be explicitly allocated within the PLACEMENT block in the link parameter file. For more information, refer to the chapter Linker Issues of the Build Tools Utilities reference manual.

The following listing exemplifies the correct usage of the CONST_SEGpragma:

/* p.h */

#pragma CONST_SEG MY_ROM

extern const int cx;

#pragma CONST_SEG DEFAULT

extern const int y;

/* p.c */

#pragma CONST_SEG MY_RAM

const int cx = 1;

#pragma CONST_SEG DEFAULT

const int cy = 2;

/* main.c */

#include "p.h"

void main(void)

{s = cx + cy;}

Find more info in CodeWarrior Help by searching "S12Z Pragmas".

Regards,

iggi

Re: Strings going to SRAM

manishsangram — Fri, 03 Jun 2016 11:49:49 GMT

Hello iggi,

Our usage of strings are more inline, meaning we are not declaring string constants at all but directly using them. For example.

sprintf("Hello World");

Why would the above string go to RAM ?