unsigned int msg[6] = {0x1234,0x5678,0x9abc,0xdefe,0xdcba,0x9876};
void func(void * msgm)
{
char a,b,c;
a = *((char*)(msgm)+0);
b = *((char*)(msgm)+1);
c = *((char*)(msgm)+2);
//printf("0x%02x  0x%02x  0x%02x\n",a,b,c); // для теста
}
void main(void)
 {
  func( &msg[2] );
 }