Open communication's protocols emerging

Jul 1, 1997 12:00 PM, By MICHAEL A. GEARHART

What are they? Who will they beneift? Should our industry use them? Here's an overview. Imagine you are the facility engineer or security manager for a multi-building site. You are required to expand the current integrated access control system and the energy management system as part of a capital construction project. As part of the last major upgrade, specific manufacturers were selected as the company "standard" for each system. Both the access control system and the energy management system manufacturer have stated that your current field panels are not compatible with the latest software. The company made a significant capital investment to standardize these two systems and to support them.

The following options are available: * request additional capital funding and upgrade both systems, or * install the latest system in the capital construction project and begin the project funding request process for a retrofit program. This results in running both the old and new systems in parallel. Such a scenario could be simplified - and made more affordable - by the use of so-called open communication protocols, which could increase dramatically end-users' flexibility in expanding their systems. This article will offer a quick overview of several communications standards currently emerging - including BACnet, LonWorks and CAB.

Two premises must be established before proceeding with this discussion. The first concerns the basic architecture of today's large multi-building access control system or energy management system. The second involves open versus proprietary systems.

Today's access control systems are composed of two basic subsystems: the transaction subsystem and the administration subsystem. Transaction subsystem

The transaction subsystem is composed of components that provide/collect data on which the administration subsystem will act (e.g., card readers, magnetic contact switches and local field panels). The transaction subsystem communicates with the administration subsystem by using low-speed, serial communication links (e.g., RS232, RS422 or RS85 protocols), or by using a LAN topology (e.g., Ethernet) in which the transaction is sent to multiple devices. The LAN operates at a much higher speed and is capable of carrying more data, but response time is determined by the LAN traffic level.

Administration subsystem The administration subsystem components accept operator commands and process information from the transaction subsystem, operator workstations and a common database. The administration subsystem is linked via a LAN to facilitate movement of large quantities of data and to control access to a common resource, such as the central database. It is not effective to distribute the database to each workstation and manually synchronize the data. The access control system will be a client-server model.

In both subsystems, an open standard is used to define the physical nature of the protocol: type of wire used, voltage levels, simple flow control, number of start/stop bits and parity. The serial communication protocol does not address the format and definition of data. The protocol defines where the data goes in the overall message structure, and how long the data is, but it does not define the data. Each system manufacturer defines a proprietary message format.

You should make a distinction between open systems architecture and proprietary systems architecture. * Open systems architecture: a system or architecture wherein standards are developed, published and maintained by an independent, recognized standards organization. Changes to the open system architecture standard are proposed by the standards organization, commented on by users and industry, and approved by the standards organization. With an appropriate level and certification, third parties that develop products that comply with these standards are ensured a minimum level of interoperability.

* Proprietary systems architecture: a closed system or architecture in which the underlying operation and knowledge of that system is controlled by an exclusive party and not published to the industry. Access to this information is under the direct control of the exclusive party, and third party systems can only be integrated by the exclusive party.

What is BACnet? The Building Automation Control network (BACnet) is a data communication protocol that allows building automation equipment from different manufacturers a minimum level of interoperability. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) began development of BACnet in 1987 and completed development in 1995 with the formal adoption of ASHRAE Standard 1355-1995.

BACnet is a software-only solution to address the real-world requirement of integrating different products from different manufacturers. BACnet consists of a standardized set of messages that replaces the proprietary messages between the field panels and the host.

BACnet is also a recognized standard of the American National Standards Institute (ANSI) and is being considered by some international organizations. The National Institute of Standards and Technology has developed a BACnet device compliance testing facility in Gaithersburg, Md.

What is LonWorks? LonWorks was developed in 1990 by a joint venture between Toshiba and Motorola. LonWorks represents a complete hardware and software solution for control network communication. The hardware platform was originally based on the Neuron chipset, which provided I/O processing and data communications. Software is based on the LonTalk communication protocol, which provides a set of standardized messages and a development tool for custom applications.

In its original implementation, LonWorks could be considered a proprietary system; use of the hardware and software required a licensing agreement from Echelon Corp. Since that time, Echelon has allowed users to port LonTalk protocol to a number of different hardware platforms that provide a significant performance increase over the original 8-bit processing capability.

To further enhance and support the openness of LonWorks, the LonMark Interoperability Association was formed in May 1994. Its goal is to develop and implement open interoperable control products and systems based on LonWorks technology.

As late as September 1995, the LonTalk protocol has the widest application base in industrial controls.

BACnet and LonWorks are not interchangeable terms. Each provides its own standardized set of messages. The commonality between the two is that BACnet messages can be transmitted across a LonWorks communication backbone. BACnet recognizes LonWorks as a physical medium only. Messages between LonWorks and BACnet are not interchangeable.

What is CAB? A 1985 study conducted by Public Works Canada confirmed the need for a simpler, more cost-effective means of operating and managing the diversity of proprietary control systems used in public buildings. Development began on a new operator workstation that would simplify day-to-day building operation and reduce operator training, particularly in multiple-vendor installations. A new, non-proprietary data communications protocol was required to link this workstation to the range of proprietary building automation systems in use.

Following years of design effort and liaison with building owners and building automation systems vendors, the first release of the Canadian Automated Building (CAB) Protocol was published in 1992. In their offerings, vendors have been encouraged to include support for the CAB Protocol with support from Public Works and Government Services Canada (PWGSC). A number have responded positively. Compatibility with this protocol is now mandatory for all new building control systems procured by PWGSC.

The CAB standard has been used for several years on government projects under the direction of Public Works Canada. The protocol handles daily operations and has file transfer capability between operation workstations and multiple vendor systems or nodes.

CAB uses a Local Area Network between gateways and workstations. It also defines a standard interface console that connects to the LAN and communicates to nodes via defined messages. CAB provides user interface capabilities across multiple-building systems and numerous buildings.

Goal: Interoperability Each of the previous communication protocols implements the goal of interoperability between various manufacturers' products, primarily via a standardized set of messages. This standardized set of messages ensures a minimum level of interoperability. At this point, the end-user may make a price-based purchase after determining that the minimum level of interoperability meets his requirements. The end-user may also make his purchase based on added value, which could range from size and stability of the product or company to enhanced functionality or performance above the minimum level of interoperability.

The standardized communication protocol allows the data collection (the transaction subsystem) to become the commodity. The operator interface is where the value or enhanced functionality is required. In the case of a system retrofit, you can reduce the additional expense as much as possible for retraining operators, revising report formats, and rebuilding links to other external systems. The converse of this could also apply where an enhanced operator interface is desired, while leaving existing field panels untouched.

Meanwhile, what can the facility manager and security manager do about the capital construction project?

First, the facility engineer and his design team will recognize the move to an open communications protocol with the energy management system area. During the last major system upgrade, a system was selected that supports an open communications protocol to the field panel. As part of the current capital construction project, the construction specifications will require compliance with the open communications protocol for the energy management equipment provided.

The security manager will review the project budgets with his design team to determine if it is more cost effective to * request additional capital funding and upgrade the existing system, or * install the latest system in the capital construction project and begin the project funding request process for a retrofit program. This results in running both the old and new systems in parallel.

In reality, our security manager has no choice, because most, if not all, access control system manufacturers support only their proprietary communication protocol.

In the past few years, the security industry has come a long way in opening up proprietary systems so that information can be transferred in and out. This openness provides the customer with increased value and greater flexibility. The communication between the file server and field panels is the last proprietary area. The use of a standardized communication protocol in this last area would provide the customer with even more value and greater flexibility.

- ABOUT THE AUTHOR Michael A. Gearheart is a control systems engineer employed by Lockwood Greene Engineers, Spartanburg, S.C., and a member of Access Control & Security Systems Integration's Editorial Advisory Board.

- FOR MORE INFORMATION Additional information about BACnet (ASHRAE Standard 135-1995) is available from ASHRAE at 800-527-4723. Information about LonWorks is available from Echelon Corp. at 800-258-4566. Echelon produces the LonWorks hardware and licenses the software. For information about CAB, call 613-234-6494.

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