The design of multiplex speech calling system is using the knowledge of digital communications that include time divide multiplex and AMI encoding and decoding etc.Host using the FPGA to control the chip TP3067 of PCM encoding and decoding to sampling the speech,then it accomplished that four branches of 64Kbps into one data flow of 256Kbps and accomplished that AMI encoding.The slave receive the code and using FPGA to decoding and demultiplex the data flow,then comeback the data flow to speech and put it to input.
At first,this paper introduce the general situation of digital communications.Then show the design process of the system hardware minutely.and show the method and design flow of FPGA ,then introduce using this method to design multiplexer,demultiplexer,AMI encoder and decoder,controller of PCM encoding and decoding chip module etc. lastly,follow the standard design flow carry on gate circuit grade of overall test．
Key words : time divide multiplex;multiplex;demultiplex;FPGA;AMI encoding and decoding;PCM
