ISDN uçbirimi veri kapısı arabirimi yazılımı

Abstract

ÖZET Tümleşik Hizmetler Sayısal Şebekesi (ISDN : Integra ted Services Digital Network) ses, veri, grafik, görüntü gibi çeşitli iletişim hizmetlerini standart arabağlar üze rinden kullanıcıya sunan ve uçtan uca sayısal bağlantı ola nağı sağlayan bir şebekedir. ISDN' e geçiş aşamasında, şu an kullanılmakta olan geleneksel veri uçbirimlerin de ISDN 'e bağlanması sağlana- bilmelidir. Bunun için veri uçbiriminin çıkışını CCITT 1.430, 1.441 ve 1.451 önerilerinde tanımlanan ISDN uçbiri minin S arabağı çıkışma dönüştürmek gerekmektedir. Tez konusu olan Veri Kapısı Arabiriminin bir par çası olduğu abone donatımı (ISDN uçbirimi), kullanıcının CCITT 1.430, 1.441 ve 1.451 önerilerinde tanımlanan S-ara- bağına çıkmasını ve şebeke sonlandırıcı üzerinden şebekeye erişmesini sağlamaktadır. Tez konusu olan Veri Kapısı Ara birimi Yazılımı CCITT I serilerinde tanımlanan çağrı denetim yordamları so nucu elde edilmiş olan B kanalında, ECMA 102 standardını dayanak olarak önce etkinleştirme yordamını başlatır. Bu yordam başarıldığında B kanalı ve veri uçbirimi arasın da iki yönlü veri iletişimi kotarır. iletişim sırasında asenkron hızdaki veriyi 64 kbit/sn kanal hızına dönüştür mek için Hız Uyarlama Yordamını yürütür. Veri aktarımı so nucu B kanalında etkinliği durdurmak üzere durgunlaşma yor damını başlatır. (v)

ISDN TERMİNAL EQUtTMENT DATA PORT INTERFACE MODULE SOFTWARE SUMMARY Integrated Services Digital Network (ISDN) supports a wide range of communications services such as image, voice, data, text and presents standart interfaces and digital end to end communications facility to the user. On the way to ISDN several steps will be follwed. First, ISDN terminal equipment will communicate over conventinal networks through Local ISDN network, then the last step will be communication over ISDN through Local ISDN network. Meanwhile, it must be supported that conventional terminal equipments be connected to ISDN. This is performed by using TAs which convert conventional interface (V.24, X.21, X.25, etc.) to S. In ISDN Project Department of TELETAŞ, an ISDN terminal equipment (ITE-1) has been designed which provides voice service and contains functions which support data terminals with asynchronous V.24 interface. The subject of this study, ISDN Terminal Equipment Data Port Interface Module Software, is designed on this ITE-1 prototype. Section 2 views ISDN concept generally. It defines the interface between user and the network, describes reference configurations and channels on the interface. In ITE-1 design, basic interface structure which compounds 2 64 Kbit/s B channels for transporting user data and a 16 kbit/s D channel for signalling is taken into consideration. Section 3 is about ISDN Terminal Equipment designed at TELETAŞ. Basic hardware of ISDN terminal eqiupment prototype (ITE-1) consists of a microcontroller (80186), a serial communication controller (82530) and a Digital Loop Controller (29C53). (vi)80186 is an advanced microprocessor whose architecture is made up of an enhanced 8086 Cpu, a chip select logic, two independent DMA channels, three programmable timers, a programmable interrupt controller and a clock generator. Serial Communication Controller (SCC) is a dual- channel, multi-protocol data communications peripheral. The device also contains on chip boud-rate generators, has facilities for modem controls on both channels and provides a Block Transfer mode to accomodate CPU block transfer Functions and DMA controllers. Digital Loop Controller (DLC) is an advanced, multi-channel, multi-protocol İATC Telecom tranciever. DLC provides an activation/deactivatin protocol based upon CCITT Rec. 1430, 144 Kbit/sn effective data transfer rate, ÎATC Telecom product family compatible SLD interface, CCITT Rec. 1.430 compatible S interface HDLC packetizing/ depacketing for D-channel data. ITE-1 software is based upon layered structure of OSI Reference model and is combined of Physical Lager (PHL), Data Link Layer (DLL), Network Layer (NWL), User Interface Module (UIM) and Management Entity (ME). PHL performs activation/deactivation of S bus and D-channel data packetizing/depacketizing. DLL applies LAPD (Link Access Protocal on D channel) which handles HDLC frames and performs error detection and correction. NWL executes call control procedures on D channel to handle network connections, UIM presents at interface between the user and the terminal equipment, getting use of a keyboard and an LCD display. ME consists of functions which service to interrupts, handle I/O of ITE-1 and perform interaction between modules. Section 4 describes how a data call on ISDN terminal equipment starts and ends. In an out going call, user enters his data call request and asynchronous communications parameters from keyboard. In an incoming call, user is informed by a message on the display, about the request of the peer entity. Data call is setup on D channel and a B channel is obtained as a result of call control procedures defined in CCITT Rec. 1.430, 1.441 and 1.451. Then data transfer setup procedure begins on B channel. When this procedure is successed, user is informed about the data transfer being started. At the end of data call, 4 types of disconnection may be initiated. (vii)User may enter call disconnect request from console or he may close his terminal. Incoming disconnection requests may also come via D channel sipnalling or B channel frames. User must also be informed about the disconnection of the data call. Section 5 defines data terminal and ISDN terminal equipment interface. This interface may be a V.24, X.21, V.24 interface for asynhronus terminals is supported. Section 6 defines Data Port Interface Module (DPIM) and the modules that create DPIM. DPIM can be handled in 3 parts : - Handler for data transmission from data terminal (DTE) to B channel (Transmitter). - Handler for data transmission from B channel to DTE (Receiver). - Handler for status control and timer services (controller). Controller is composed of the following modules : - Status Control Procedure (SCP), - Timer Service Module (TSM). SCP is a finite state machine which has 3 phases as activation, data transfer and deactivation. It works in coordination with serial Communications Controller and handles the interrupts that SCC creates. Interrupts because of status changes is handled in SCP and transfered to other modules via flags. Interrupts because of tranmitter and receiver are used for calling related modules. TSM is responsible of starting and stopping 4 timers on request from other modules. It also calls the module that request timer service, on the expiry of the timer. Transmitter of DPIM is composed of the following modules : - Tx Frame Preparing Module (TFPM), - Tx Frame Queue (TFQ) and TFQ Handler, (viii)- Ones Frame Queue (OFQ) and OFQ Handler, - Break Frames Queue (BFQ) and BFQ Handler, - Tx B-channel Data Handler (Tx BDH). TFPM is invoked at every received character from data terminal (DTE) and it converts the received character and status of asyncronous port to the 80(40) byte frames, defined in ECMA-102, whose adress it obtains From TFQ. TFQ Handler is responsible of adding the frame it gets from TFPM to the stream of valid frames, and returning the address of the frame at the beginning of this stream, when its called from Tx BDH. Tx BDH is invoked upon interrupts from transmit DMA channel. It is a finite state machine with activation, data transfer, loss of frame synchronization and deactivation phases. According to the flags writen by SCP, FRAM and RWQ and to return value it gets from TFQ, Tx BDH transfer the frames whose adresses it gets from TFQ, OFQ or BFQ or the activation or the deactivation frames. modules Receiver of DPIM is composed of the following. - Rx B-channel Data Handler (Rx BDH), - Rx Frame Queue (RFQ) and RFQ Handler, - Rx Frame Analyzing Module (RFAM), - Rx Word Queue (RWQ) and RWQ Handler, - Rx Data Port Handler (Rx DPH). Rx BDH is invoked upon interrupts from receive DMA channel. It transfers the received frame from B channel to RFQ and activates the CTS input of SCC. RFQ is responsible of adding the frame it gets from Rx BDH to the stream of valid frames, and returning the address of frame at the beginning of this stream, when it is called from RFAM is a finite state machine with 4 phases which are activation, data transfer, loss of frame synchronization and deactivation It analyzes the frame it gets from RFQ and writes the status changes to the related flags and the characters and status it obtains from the received (ix)frame to RWQ is responsible of writing the characters and status it gets from RFAM to RWQ and returning the word at the beginning of RWQ when it is called from Tx DPH. Tx DPH is invoked when every character is transmitted to DTE. It transfers the character it gets from RWQ to SCP. ISDN terminal equipment, this study is designed on, is a laboratuary prototype and open for enhancements in the future. In this study, data call is setup from console and a B channel, gained via D channel signalling, is presented to the data terminal. In the further studies, data call may be started from the data terminal. In that case, signalling performed by data terminal is converted to ISDN D channel signalling. Data terminal gains a B channel and starts data transfer. V.24 asynchronous interface is supported in this study. It is expected in the future applications that X.20, X.20 bis, X.21, X.21 bis and V.24 synchronous interfaces are also supported. ECMA 102, this study is based on, performs data call in the following way. Users communicate with each other via voice service. After they agree on parameters, they end the voice session and use the same channel for data transfer. When data transfer comes to an end, the same channel may also be used for voice communication. This implementain is not supported in CCITT Red Book, but it is informed that Blue Book contains this alternate voice/data call. In the future, the design will be modified» ^according to the Blue Book. (xi