Dual Ethernet stack for maximum speed access to a PLC

#Applicants' invention relates generally to the field of programmable controllers and more particular to a system for coupling a network of programmable controllers through an internetwork to a monitoring and control device.

#Remote monitoring and control of systems and process have taken many forms. In the past, dedicated lines became the most common form of communication between a control system and a remote location. This has limited application since the control system was not accessible from multiple locations. Modems have made it possible to access the control system from different locations, but these types of systems are generally restricted to downloading and uploading data files. Providing any type of control function between locations is rather limited in this type of environment. Further, an end user generally required a customized interface to access the control system.

#With the growth of Internet, and its World Wide Web providing a deliver platform for organizing Internet data through hypertext links, a client server system can be designed that will give each end user the same type of a user friendly interface with the same universal access to services on the Web. The Web is a network of documents called sites or pages stored on server computers throughout the world Each page will usually contain text, some type of multimedia offerings such as graphic images, video, or audio, and possible hypertext links to other documents. A browser allows a user to read the pages and interact with the choices associated with it. The browser is a graphical software program that sends commands to the Internet Web site and displays whatever information is available on the page. Various browser programs are commercially available from different manufacturers.

#FIG. 1 shows an overview block diagram of a typical system illustrating the relationship between an user at a remote location and an Internet Web site used for monitoring a process control system according to the present invention.

#FIG. 2 is a basic block diagram of the present invention illustrating an Internet interface to a programmable logic controller system.

#FIG. 3 is a block diagram of the Web server module illustrated in FIG. 2 according to the present invention.

#Although this invention is susceptible to embodiments of many different forms, a preferred embodiment will be described and illustrated in detail herein. The present disclosure exemplifies the principles of the invention and is not to be considered a limit to the broader aspects of the invention to the particular embodiment as described.

#FIG. 1 shows an overview block diagram of typical system illustrating the relationship between an user 2 at a remote location and an Internet web site 4 used for monitoring a process control system 6. The user 2 will have a personal computer (PC) 8 having a commercially available browser 10, such as Netscape Communication's Navigator or Microsoft's Internet Explorer, installed for viewing the contents at the web site 4 by a monitor 12 through a network, such as the Internet 14. The PC provides a remote human-machine interface (HMI) to the process control system 6. Various interconnection services are readily available to provide the physical and electrical interconnection from the PC to the Internet 14 itself. The Internet 14 is a collection of independent world wide communication networks that are interconnected to each other and function as a single connectionless entity. Communication is based on a client-server basis, using a number of established protocols that allow for communication and file transfers between the client and the server. The most widely used protocol is Internet Protocol (IP).

#The web site 4 includes a network interface 16 having an unique Internet address 18, a server 20, and an application program 22. The server 20 acts as a hypertext transfer protocol (HTTP) interpreter which uses Transmission Control Protocol (TCP) in conjunction with Internet Protocol, through a Transmission Control Protocol/Internet Protocol (TCP/IP) stack 24 to interact with the network interface 16 and the application program 22. This enables the data transfer between the application program 22 and the user 2 through the Internet 14. The application program provides data from the process control system 6. This data can be used to monitor the control process by the user 2 at the remote location. The stack 24 enables data transfers over the Internet 14 between the user 2 and the web site 4 as required for the various layers specified by the IP protocol.