| How to realize transmit voice, data and image becomes an important and in dire need of solving issue. Intelligentize digital terminal can solve it for enterprises. Intelligentize digital terminal-LAN telephone system is make of LAN telephone terminal and gateway. Gateway is the key equipment for LAN telephone communicate with the Public Switched Telephone Network, it affect the performance of the system directly. So, develop of the LAN telephone gateway has application value.The design of LAN telephone gateway includes two parts: hardware and software. The design and implementation of the system are presented in this dissertation, of which hardware design, implementation and debugging are described in detail. The design and implementation scheme of each section was analysis in detail in this dissertation, and discussed the design and emulate process of PCM interface. At the end of this dissertation give the result of debugging and testing.The contribution of this dissertation:Firstly, use Complex Programmable Logic Device (CPLD) connect with ISA bus of computer. In this dissertation, this function was performed by a piece of EPM7128S chip in series MAX7000, to implement the data transmission between circuit and computer.Secondly, the PCM interface was transformed by CPLD logically. Use CPLD, we can get Time Sharing what need for circuit conveniency, simulate and validate it.Thirdly, to design gateway control by GAL apparatus. I use logical program to design GAL in this dissertation, the pin can defined agility, this made the structure of circuit compactly and connect simply.Finally, an approach to recognize DTMF is proposed. Aimed at the character of DTMF signal, this algorithm is to get the DTMF signal according to compare the value of energy based on DFT.The successful execution of the terminal designed in this dissertation proved this design is logical and the implementation is successful. |
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