Question

I have a 32 bit long variable, CurrentPosition, that I want to split up into 4, 8bit characters. How would I do that most efficiently in C? I am working with an 8bit MCU, 8051 architectecture.

unsigned long CurrentPosition = 7654321;
unsigned char CP1 = 0;
unsigned char CP2 = 0;
unsigned char CP3 = 0;
unsigned char CP4 = 0;
// What do I do next? 

Should I just reference the starting address of CurrentPosition with a pointer and then add 8 two that address four times?

It is little Endian.

ALSO I want CurrentPosition to remain unchanged.

Answer 1

    CP1 = (CurrentPosition & 0xff000000UL) >> 24;
    CP2 = (CurrentPosition & 0x00ff0000UL) >> 16;
    CP3 = (CurrentPosition & 0x0000ff00UL) >>  8;
    CP4 = (CurrentPosition & 0x000000ffUL)      ;

You could access the bytes through a pointer as well,

unsigned char *p = (unsigned char*)&CurrentPosition;
//use p[0],p[1],p[2],p[3] to access the bytes.