With the continuous development of the telecommunications industry, Modem has become an important part of people's live. Modem have earlier experienced the development of non-smart to smart, from low to high-speed, from analog to digital data communication from a single data / image, voice communications, phase change, it can be said a lot of today's modem is a high crystallization technology.
This thesis talked about a design of FSK modem using AT89S51 MCU, in accordance with the principle of FSK modem, choose AT89S51 microcontroller, through the PC serial communication with the microcontroller, the design of the CCITT V2.1 agreement modem, with emphasis given to the modem to achieve the C language program from the software to achieve the functions of a modem. In addition, in the same group of students to complete the hardware circuit of the debug process, the validity of the procedures in the actual feasibility of the hardware circuit.
Keywords: frequency-shift keying, modulation, demodulation, AT89S51 serial communication