Accessing A Memory location using Pointers in Embedded C

In microcontroller programming we have to write or read certain registers. The questions is how to access these registers ?.

The register or a memory location can easily be accessed using pointers if we know the required address. But, From where we can get theses addresses ?

The reference manual of the microcontroller contains all the details regarding address of different register or required memory locations. Let's consider we have a 32 bit microcontroller and the objective is to write data to a register having address : 0x00040002 (32 bit address)

Code:

# define addr 0x0004002

main()

{

unsigned long *p; /* As the pointer needs to store 32 bit address */

p = (unsigned long *) addr; /* Assigning Address to the pointer*/

*p = data; /* Writing data to the memory location specified by the pointer*/

return 0;

}