global variable assign RAM address

Question

I am writing C code for an MSP430 microcontroller and I want to lock a global variable to a specific address in RAM.

The reason is because I have a stack at the end of the RAM address and grows downwards towards lower addresses. When the stack overflows, it starts overwriting global variables stored in RAM right next to the stack. So I want to write a watermark that is right next to the stack and check it for overflows.

Answer 1

If you know where the end of the stack should be on your MSP430 device, you could do this, for example:

int* ptr;           // will point to end of stack
ptr = (int*)0x0600; // memory address of the end of the stack
*ptr = 0x1234;      // value to assign to memory

Here's someone that has your same question, on the TI forums... it looks helpful: http://e2e.ti.com/support/development_tools/compiler/f/343/t/92002.aspx

Answer 2

StackWatch & StackIntact MSP430 code for Code Composer Studio

#include <string.h> // C string functions

unsigned int StackWatch(unsigned char fill);//prototype

const char stackstr[]="#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=#=";
//^stackstr needs to have enough characters to cover the size of stack 'intactness' you desire

#pragma DATA_SECTION (_stackTAIL, ".stack");//locate this variable at the stacks end (lowest address)
const char _stackTAIL;//don't futz with this variable //DANGEROUS

unsigned int stacktail=0;

unsigned int StackWatch(unsigned char fill)
{
 if (stacktail==0)
     {
         stacktail=(unsigned int)&_stackTAIL; //debugging
         strncpy((void *)stacktail ,stackstr,fill);
     }
 if(fill==0)stacktail=0;//discard the pointer

 return stacktail;
}//StackWatch



unsigned char StackIntact(unsigned char CHRS)
{
     if (stacktail==0)return 0;

     if (CHRS>strlen(stackstr))CHRS=strlen(stackstr);

     return strncmp((void *)stacktail, stackstr, CHRS);

}//StackIntact

////USE IT LIKE THIS>>
//in main only once as close to the beginning as possible..

//StackWatch(20); ///Make sure you have enough chars in the stackstr const...


//in a loop somewhere>>

//if(StackIntact(20))
//.ERROR CONDITION.//blink led or something..

//if it doesn't ==0 then the stack is not intact for that many characters

//////////////
//WHEN YOU ARE DONE WITH IT>>
//StackWatch(0);//discards the pointer to the end of the stack 

Originally posted here http://forums.hackaday.com/viewtopic.php?f=5&t=2998

I don't know that I'd leave it in production code but it really comes in handy for Debug code

maybe...It would probably come in handy to reset if something went awry but i think it would just happen again so really pointless in production quality code yes, you can do this through CCS and whatnot but thats a PITA as well

Also Note this is for CCS (Code Composer Studio) #pragma DATA_SECTION (_stackTAIL, ".stack") is a compiler specific name and pragma so you probably will need to use a different method of grabbing the address such as that suggested above