RTSJ is an improvement document for Java in Real-Time System. It talks about how to install RTSJ and use it at first. Then, it comes to the circuit design part. Because there is no devise, which can achieve RS232 serial port to 8 bits parallel signal, on market, it has to be designed by ourselves. After that, this report shows the Java classes in this project and introduces them separately. At the end of the main body of this report is the result and conclusion. In a word, this project has not been finished yet and the future work of this project is very important to achieve the final target.