| With the continuous development of the embedded system, the problems of equipmentnetworking, remote monitoring, data transmission need to solve. Currently, there are two solutions.One is takeing the devices access to the Internet with the Ethernet (RJ45) directly; another is usingembedded modem by the serial port (RS232).This paper introduces the development and current situation of modem, describes thedevelopment and characteristics of the embedded system, and gives the definition of embeddedmodem. Puts forward a method of embedded modem based on CMX469A, which is a scheme todata transmission for Nanchang Lutong high and new technology LLC.This design is mainly used for communication between acquisition module and the workstationthrough the erection allon the railway line. The scheme which is based on embedded system usesthe CMX469A modem chip to realize the purpose of4800BPS full duplex modem. For the51series microcontroller which only has one serial port, as the CMX469A does not take up serial port,the single chip microcomputer serial port can be used conveniently for serial communication withcomputer or other equipment. This provides the convenience for design of whole system.The design of the embedded Modem has the following advantages:(1) Small volume. Because the main part of the embedded Modem is SCM and Modem chip,and components composed peripheral circuit are packaged by SMT type, the overall volumecontrols in a very small range, and saves much space.(2) Simple peripheral circuit. The component embedded Modem function modules areintegrated into a chip. Peripheral circuit just concludes some necessary voltage regulator, filteringand rectifier functions. So a simple circuit can achieve its function.In addition, the Modem realized with CMX469A has advantages such as strong anti-interferencecapability, simple circuit, conveniently programming and low cost. It is easy to install and maintainas well.This design is summarized and prospect at the end of papper. |
