Based On The N-isdn Digital Subscriber Terminal Communications Systems Research And Design

In recent years,along with the fast development of economy,the users' demands of data communication is increasing fast,a large number of small scaled digital program-controlled exchange device are widely used by many organizations,corporations and mineral enterprises...ect. The type of these device generally offer the function of auto-exchange,connection,conference and coordinate.They can realize the inner call and can also connect into the public exchange network.Most of them only provide the traditional analog interface to users,analog signal is transmited across the line between the user and the exchange,the rate is lower and is easy to be interfered. So the mainly function offered by the private telecommunication network built up with them is limited only in voice service fields.The Service is simple and the function is simplex.Therefore for overcoming the weakness of network connecting,and satisfy the increasing demands of users in the private telecommunication network,many of these exchange device should be reformed or upgraded.The exchange in this thesis belongs to this type.ISDN(Intergrated Services Digital Network)User-Network technique is a kind of advanced technique of user interface numerical. So this paper chooses ISDN exchange as reference model and gives the full resolution.We add the digital user interface board to the program-controlled exchange developed by our own school to realize the numerical of the user interface.This paper expound the basic theories and related protocol of ISND User-Network interface and analyze the project of designing the hardware and software of the digital user interface board.This paper follows the principle which combines hardware and software.choose MC145572 which produced by Motorola to carry out the physical connection on the U node of N-ISDN.Realize the whole ambilateral communication on the user line and the 2B+D data rate reaches to 144kbit/s.Adopt PT7A8952P to carry out part of the protocol on data link level. Most of the logic work are carry out by CPLD(Complex Programmable Logic Device) on the board to insure the fastly,efficiently and dependable of the system,After getting reformed,the exchange can offer voice,data,image transmission services.It can satisfy the increasing user demands.Meanwhile the resolution discussed by this paper keeps the old exchange framework at the most benefits and can be applied to other model small scaled digital program-controlled exchange easily.