GFK-2224Q January 2017 199Chapter 11 RX7i PLC Monitoring Via the WebThe PACSystems RX7i embedded CPU Ethernet Interface provides PLC data monitoring using a standard Webbrowser. Rack-based Ethernet modules and the RX3i embedded Ethernet interface do not support web serveroperation.You can use the Web server to monitor the following PLC data:▪ PLC reference tables. This data is a snapshot of the PLC Reference Tables when the data is displayed inthe Browser and is not updated until you request another display. All reference tables are supported.▪ PLC and I/O Fault Tables.The web server cannot be used to modify PLC data (acknowledge alarms, set/force values in tables).The maximum number of web server connections that can be configured for the Ethernet Interface is 16. If thesystem includes FTP server connections, fewer web server connections are available, as explained in 0.11.1 System RequirementsWeb monitoring requires version 4.0 or later of Netscape Navigator or Internet Explorer. The browser must becapable of running the Java Virtual Machine (JVM) version 1.3 plug-in. The supported host operating systemsare Windows NT 4.0 SP5 or SP6, Windows 95B, Windows 98 (First Edition Service Pack 1, Second Edition), andWindows 2000 Professional SP1, Windows Millennium Edition, Windows XP and Windows CE 3.0. To view theentire Reference Table page, the screen resolution must be 1024 x 768 or higher. Local web firewall blockingissues will be avoided by using HTTP protocol on port 80 to transfer standard HTML files including JavaScriptand Java applets from the server to the browser and HTTP Post command to transfer form information fromthe browser to the server.11.2 Disabling Pop-up BlockingMost internet browsers provided a feature that blocks pop-up windows. This prevents the viewing referencetables. Change your browser settings to permit pop-ups.11.3 Web Server Operation in a Redundant SystemIn a redundant system, only the active unit processes Web Server requests at the Redundant IP address andresponds to web page requests. The backup unit does not respond to the Redundant IP address. When theactive Ethernet interface changes to backup, it takes down all Web Server connections and their underlyingTCP connections. The Web Server maintains its underlying TCP connection only long enough to process eachweb page request; a new TCP connection is opened, used, and closed for each subsequent web page display orupdate. Unless a web page change or update is requested during a redundancy switch, the operation of theRedundant IP address is transparent to the Web browser. Any web page request in process over theRedundant IP when a role switch occurs is ended.Although both the active and backup units respond to Web server requests received at the direct IP address,having a remote (host) browser issue Web Server requests to the direct IP address is not recommended.Remote web browsers should use the Redundant IP address when communicating to a Redundant System.11.4 Standard Web PagesThe CPU Ethernet Interface is shipped with a set of standard PLC web pages already installed. These standardweb pages include a PLC home page, a Reference Table display page, a PLC Fault Table display page, and anI/O Fault Table display page. When necessary, new or revised web page files may be transferred into theEthernet Interface via the standard FTP protocol, as described later.
