Take a look at the end of this thread. In particular, look at Lundin's post. He provides the C code of a routine that converts a 32-bit int into characters. It should be suitable for your use.
Basically, I have an integer (16-bit) that I want to send over the serial port. I have routines that send the value of a char (8-bit) and a string (multiples of chars). So I'm looking for a way to either divide an int into two chars. Hope it's clearer now.
Take a look at the end of this thread. In particular, look at Lundin's post. He provides the C code of a routine that converts a 32-bit int into characters. It should be suitable for your use.