Study, Based On The Design Of Embedded Instrumentation Bus Communication Interface

M-bus , as a Europe standard of water meter ,gas meter,and electricity meter, has attracted wide attentions in instrument field. The mechanism of m-bus communication and its embedded master and slave interface for communication are researched.As a toll-gate between bus and terminal unit, bus interface should meet all those requirements of M-bus such as :communication protocol and feature of data transmission. Therefore, it is necessary to research the communication protocol for M-bus before commencing bus interface. As the same with the Fieldbus, the protocol is based on ISO-OSI (International Standard Organization-Open System Interconnection) , but it is not different from Fieldbus in many aspects, above which are designed a management layer to control the parameters of address , baud rate and so on.At the other hand, in order to integrate the signals from different terminal instruments into M-Bus system , for instance AMR (Automatic Meter Reading system) ,there are two ways to fellow :a) .Designing terminal instruments according to the same prescriptive standards;b). Developing a special bus interface so as to link terminal instruments and M-Bus system.For the purpose of the paper, great efforts are made to research the process of bus interface dealing with data ,such as the basic principle of data transmission , interface forms and the requirements including physics features, data link, data ID (identification),data security and data format. All those can get the result that they benefit to help data link between slave station and master station unseallingly.The design of the embedded interface for communication is one of the key parts and difficulties in the process of researching M-bus. It includes master interface and slave interface. The function of master interface is to convert the RS485 voltage into M-Bus voltage so as to supply terminal instruments and to search, read, manage up to 250 terminal instruments. Meanwhile , the function of slave interface is to convert the data from terminal units into M-bus pulse signal according configuration of pulse increment and unit of different terminal instruments. For structure, master interface includes power supply module, transmitter module, receiver module, overload warning module, and repeater module; slave interface includes MSP430 micprocessor module and Microcontroller --TSS721A transceiver module. For signal modulation, it is modulated by voltage from master to slave and by current from slave to master, what is most important is that data transmitter and power supply share one signal line .In the process of soft designing, the keys are to search slaves according Wildcards and exchange character between interface and terminal instrument. The related flow diagram and principle diagram about soft and hard designing are given in the paper.There are some innovations in the fellowing aspects:a) Integrating water meter ,gas meter,and electricity meter into one system;b) Soft and hard designing.