Well, connecting the l298 chip to the AT89S52 is very simple, you can treat the driver exactly as a series of BUFFER gates. it's pretty easy to catch from the datasheet.. Each gate(channel) can be connected to a wire of the stepper motor from one side, and to a pin of the micro controller from the other side.. then, a 1 on that pin will cause the equivalent power output to go HIGH
if you don't know what to do with the Current sense pins, you can connect them to GND, it's not recommended, but depending on the size of your stepper motor, it can be acceptable..