Study Of The Access Technology Of DDN

Digita1 Data Network (DDN) is a digita1 transmittingnetwork that transmi ts data by digital channe1s. Now thebackbone network of DDN ifl our coufltry has covered over 30 bigcit 1es of China, i. e. most users may efljoy the services of DDN.But in some sma11er cities or remote areas, DDN 1s not verypopu1ar because the insta11at ion and p1acement requi rementsof DDN equipments iflcrease the user's costs.The object studied in this paper is an embedded functionalmodu1e of SP30 sw1tch system produced by Xi' an DatangTelephone Corp. It can provide various service intelfaces ofDDN for users. It's ca11ed data service access system. Fromphysica1 v1ew, it extends the interfaces of DDN services toremote customer's sides by SP30 and its transm1ssion network.It forma1ly combines DDN and PSTN (Pub1 ic Switched Te1ephoneNetwork) into one cabinet and makes popu1arization of DDNpos s ib l e.The author has put forward the structure of data serviceaccess system in this paper. It is designed by util izing theSP30 swi tch's advantage of convenieflt to add new serv ices andfunctions owing to 1 t s opening bus structure, and by the methodNjL1:}thk{Pfi! ff9uitkof connecting to DDN via 1eased 1ine of 2048 k bits / sec. 1t1s desigfled 1n the structure of main board with sub--boards ofservice iflterfaces or maifl/sub--board with sub--card of aservice inter f'ace. It meets the requirements of various kindsof network comDos it ion for differeflt users in f1exible way.The author has finished designs of the system, inc1udingits important modules and two ASIC chips of DTV35 & DTX50. Aseries of key techniques have been so1ved as we11. Now we havecompleted this design. The system has passed the qua1ityva1 idat iofl of our compafly and fina1 1 zat ion for both des ign andproduct ion. Bes ides these, it has a1 so successfu1ly connectedwith the equipments of DDN produced by New bridge corp. andGDC Corp, and it works ok in Yun Nan, Shi Jia Zhuang, Shan Xi,Hu Nan and Hang Zhou etc. It not only increases the marketcompetitiofl abi 1 ities of our products but a1so has gainedquite good profi ts for our company.According to the requirements of customers we wi 1l make thekinds of interface abundant and increase the communicatioflspeed. 0n the other hand, we wi 11 design embedded synchronous--to-- asynchronous converter so that users can use our systemeas i 1 y.