【文章內(nèi)容簡介】 Input, Output or, Memory that the system is using. Pointers represent addresses for Input, Output or, Memory.? A Pointers reading table used to store the values read from items pointed to by the various pointers. This table is similar to a log table that holds the various stations activities.? An Admin table contains all the information on system users. A Rank attribute indicates the security level for each administrator, such as, Main Admin, Supervisor, and Trainee. Additional information include login name, password, a Hint attribute for password recovery, etc.? A Client table contains all the information pertaining to each client that is using the system such as user identification, password and phone.? Admin_PLC and Client_PLC tables used to set the corresponding admin or client to a specific station id, and pointer id.. Application modulesThesemodules are at the heart of the software ponents of the overall system. They manage the munication between the user interface and the DBMS. They initiate the connection to the PLC system and contain the needed objects for GSM munication.The application modules consist of following three submodules:Fig. 5. A GUI display.? A data manipulation module: this module has several classes that are called from within the user interface (GUI) to perform various data manipulation tasks within the database such as: insert, update, and delete. For example, the insert class is responsible of inserting any new data received through the user interface.? A PLC munication module: this module consists of three classes。 they are used to perform tasks such as accepting stations ID from users, verifying that each station has a pointer associated with it, establishing connection to the PLC station, etc.? A GSM module: this module provides for the munication between the GSM modem and the munication ports. The java munication package is used. This package allows java to recognize both the serial and the parallel ports that are part of the system. It contains the necessary functions required to send and receive AT mands and SMS messages through the GSM modem.. The user interfaceThe user interface used in this work allows users (administrators and clients) to access and manipulate the database tables and to issue basic control mands to the different PLC stations. For database manipulation the administrator depending on his/her rank can insert, update, or perform different queries. Administrators can also perform other activities using this GUI such as sending SMS massages to different clients and administrators. Depending on his or her rank, an administrator can enter the configuration area, and perform activities such as viewing admin logs, viewing help documents, viewing tutorials of how to use the user interface as well as controlling some activities in the station.Fig. 5 shows one of the GUI screens of the system. The figure shows the different fields that correspond to the station table attributes. Users can enter various values pertaining to a particular station such as its IP address, its location, number of inputs and maximum number of outputs. As shown on the left panel of the GUI interface, users have the ability to search, view, configure, and update the information of a particular station. Fig. 5 depicts a GUI screen for the Update mand. Users may use this mand to modify particular station information such as its IP address, or location. Fig. 6 is a snap shot of the GUI where the user is embarking on a search task. In the shown search screen the user is searching for a PLC station by location. The response to his search request is shown in Fig. 7.4. Using TCP/IP to municate with the PLCThe CP module is a munication processor for the S7 family that allows PLCs to connect to an Intranet or the Internet in any LAN setup. The module supports the following TCP/IP munication services [7]:? Secure FTP (File Transfer Protocol) and HTTP (Hyper Text Transfer Protocol) server login with user IDs and passwordFig. 6. Sample GUI display. Fig. 7. Response screen to a “Station Search”.? Send Email messages with embedded PLC data to standard SMTP mail server? FTP client services for file transfer to a remote server? FTP server services for file transfer to/from an internal 8 MB flash memory file system by a remote FTP client? HTTP server services for remote Internet browser access? S7 series program instructions for Internet munication.In addition the module also has the following features:? Communication based on TCP/IP and ISO standards? Factory installed MAC address? Peertopeer munication capabilities with other S7 devices? Multiple (up to 8) connections? Ethernet client or server configuration options ? Program instructions for initialization, reconfiguration, and