How to point a structure to a particluar address

I am trying to point a structure to a particular memory location , can anyone please tell me how it can be done in c programming . I have defined a macro which holds the starting address of the memory location.

#define START_ADDR 0xF6000 //starting address

typedef struct {
     uint32_t checksum;
     uint16_t index[len];
} block;

I changed the memory allocation of block using the below statement:

block *value = (block*) START__ADDR;

I verified the change in memory allocation as well and no issue with it.I am working on FLASH memory and i have verified that writing operation can be done on the particular memory location which i have mentioned. Now i am trying to update the value of checksum using

value->checksum=0xa5a5a5a5;

But the value of checksum is 0x00000000 and not getting updated to 0xa5a5a5a5. Can anyone please tell me how can i change the value of checksum.

Thanks in advance.

Regards Vybhav

Considering that you do know what you are setting or landing there (and you have permissions to do that), two main ways are:

a) Derefering a pointer which points to the address:

#define ADDR 0xXXXXXX
unsigned int volatile * const var = (unsigned int *) ADDR;

Your specific case:

typedef struct {
    uint32_t checksum;
    uint16_t index[len];
} block_t;

unsigned block_t volatile * const block = (block_t *) ADDR;
block->checksum = 0;

b) Through the linker:

file.c:

block_t __attribute__((section(".theSection"))) block;
block.checksum = 0;

linker.ld:

SECTIONS
{
    .theSegment 0xXXXXXX : {KEEP(*(.theSection))}
}

Note that I have renamed the type block to block_t.