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Using Non-Volatile Memory

There are two methods how an application can use non-volatile memory. The simplest method is to declare a read/write device Region and a structure type containing all data to be placed in that region. At run time, initialize a pointer to that structure with the address of the region.

Example (in the application's configuration file):

Region  NVRAM  Start  Size  Device  ReadWrite

In the application's source code:

typedef struct { 
   int AnInteger; 
} NVRAMData; 

void main(void) 
{ 
   const RTAppSection * S = RTLocateSection(1, RT_ST_REGION, "NVRAM"); 

   if (S != NULL) 
   { 
      NVRAMData * pNVRAMData = (NVRAMData*) S->SectionAddr; 
      printf("NRAMData %p->%i\n", pNVRAMData, pNVRAMData->AnInteger); 
      pNVRAMData->AnInteger++; 
   } 
   else 
      printf("can't find NVRAM region\n"); 
}

The other method places all data to reside in non-volatile memory in a separate data segment/section and Locates that Section or NTSection to a device Region. To use this method, the compiler must support placing data into a named section. Microsoft Visual C++ supports this through the #pragma bss_seg(...) directive.

Example (in the application's configuration file):

Region  NVRAM  Start  Size  Device 
... 
Locate  NTSection  .nvram  VMem->NVRam

In the application's source code:

#pragma bss_seg(".nvram")  // start to put data in section .nvram 
int AnInteger; 
#pragma bss_seg()          // restore default section name 

void main(void) 
{ 
   printf("NRAMData: %i\n", AnInteger); 
   AnInteger++; 
}

Advanced Topics

Using the 387 Emulator

Running on a Virtual Target