Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1995-10-13
2001-10-16
Lefkowitz, Sumati (Department: 2181)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S062000
Reexamination Certificate
active
06304934
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to control systems and, more particularly, to methods and apparatus for interfacing a computer to a Fieldbus control system or network.
BACKGROUND INFORMATION
Industrial process control systems are used to control a variety of manufacturing and processing systems. To be effective, process control systems must be capable of operating reliably under a wide range of extreme and often hostile environments both in terms of physical as well as electromagnetic conditions.
Modern process control systems often comprise a variety of smart devices, such as control valves, pressure and temperature sensors and flow meters. Smart devices are generally considered to be those that include CPUs and which are therefore capable of processing control or measured information, e.g., from a sensor.
Fieldbus is a two wire, bidirectional digital communication arrangement that interconnects smart field devices to each other, to control systems and/or to instruments located in a control room. References herein to a Fieldbus refer to a bus operating according to a Fieldbus protocol. The Fieldbus communications protocol is described in FIELDBUS FOUNDATION™, Fieldbus Specification, Function Block Application Process, Parts 1 and 2, Revision PS 1.0, Apr. 27, 1995 which is hereby expressly incorporated by reference. It should be noted that while the cited Fieldbus Specification documents are useful in providing an understanding of the Fieldbus protocol, they are not prior art to the present application.
The Fieldbus digital communications protocol allows communication among a variety of smart devices, such as transmitters, valves, local controllers, sensors, etc. The Fieldbus protocol, which uses digital signals to communicate control information and data between networked devices, offers several advantages in terms of reliability and connectivity over the older 4-20 mA analog communications protocol previously used to network control system devices and sensors together.
In order to monitor or control devices coupled together by a Fieldbus as part of a network, it is often desirable to be able access the network at a convenient site, e.g., in the field near a sensor or control valve.
Accordingly, there is a need for a portable unit which can be easily attached to the Fieldbus of a control system, which can display Fieldbus information, and which can be used to monitor and program the various devices which comprise the control system.
Where a computer is used as part of the portable unit for monitoring and controlling devices attached to the Fieldbus of a control system, an interface device for coupling the computer to the Fieldbus is required. It is highly desirable that such an interface device be low in cost, easily portable, and be capable of reliably transmitting information over, and receiving data from, the Fieldbus.
SUMMARY OF THE INVENTION
The present invention is directed to control systems and, more particularly, to methods and apparatus for interfacing a computer to a Fieldbus and the devices coupled thereto.
In accordance with one embodiment of the present invention, a computer, for example, a laptop personal computer, is interfaced to a Fieldbus via a computer interface device. In this embodiment, the interface device couples the computer to the Fieldbus via a serial port of the computer.
In accordance with the present invention, an interface device is provided which can be used to couple a serial port of a computer directly to a Fieldbus to communicate data and other information therebetween.
In one embodiment of the interface device of the present invention, the interface device is designed to be relatively small, e.g., approximately 1½ inches wide, ¾ inch high and 4¼ inches long and capable of being plugged directly into, e.g., a standard 9-pin serial port connector of a computer. Because of the interface device's small size, it is well suited for use with both portable notebook or laptop computers as well as desktop computers.
In accordance with one embodiment of the interface device of the present invention, the interface device is powered not by the Fieldbus but by the serial port of the computer to which it is attached. In this manner, the computer interface device of the present invention can be coupled directly to a fully loaded Fieldbus with no concern for overloading the Fieldbus power supply. This feature permits the interface device of the present invention to be used, for instance, in a control room or in the field, for diagnostic and network control purposes, without first having to assess the existing load on the Fieldbus.
As will be discussed in greater detail below, the computer interface device of the present invention includes the above-described advantages over known interface systems and numerous other features which make the interface device of the present invention particularly flexible, reliable, easy to implement and well suited to the control system environment.
REFERENCES:
patent: 4791356 (1988-12-01), Warren et al.
patent: 5313642 (1994-05-01), Seigel
patent: 5341496 (1994-08-01), Middledorp et al.
patent: 5412643 (1995-05-01), Kogure
patent: 5442639 (1995-08-01), Crowder et al.
patent: 5458048 (1995-10-01), Hohner
patent: 5522043 (1996-05-01), Fukunaga
Fieldbus Foundation™, Fieldbus Specification, Function Block Application Process—Part 1, FF-94-890, Revision PS 1.0, Apr. 27, 1995.
Fieldbus Foundation™, Fieldbus Specification, Function Block Application Process—Part 2, FF-94-891, Revision PS 1.0, Apr. 27, 1995.
Instrument Society of America, Fieldbus Standard for Use in Industrial Control Systems, Part 2: Physical Layer Specification and Service Definition, pp. 38-51, 1992.
Campos, Jr. Lellis Do Amaral
Paravela, Jr. Claudene
Pimenta Alexandre
Prizon Delcio
Zanarotti Geraldo Sergio
Kenyon & Kenyon
Lefkowitz Sumati
SMAR Research Corporation
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