PREPARED BY REVIEWED BY TITLE:
Metasys N2 System Protocol Specification for Vendors
DATE ENG. SPEC NUMBER
N2 System Protocol Specification(For Vendors)
Last Revised: 05/10/99
Metasys is a registered trademark of Johnson Controls, Inc. Opto-22 and Optomux are registered trademarks of Opto 22. All other trademarks or registered trademarks are the property of their respective holders. Copyright 1994, 1996 by Johnson Controls, Inc. All Rights Reserved. The documentation contained herein is the exclusive property of JohnsonControls, Inc. and its use is restricted to the terms with which it is furnished. The documentation contents are confidential and may not be disclosed without the express written consent of Johnson Controls. This documentation is further protected by federal copyright law as an unpublished work and any unauthorized reproduction is prohibited. This document contains the most accurate Metasys protocolinformation available at the time of printing. Metasys protocols and data structures are subject to change. Johnson Controls does not guarantee the accuracy of this document, nor will it be held responsible for damages of any kind, either direct or indirect, which may result from the use of the Metasys N2 System Protocol Specification for Vendors, even in situations in which a Johnson Controls employeehas examined your system. Also, if and when this document is updated, Johnson Controls will not necessarily send you a revised copy. Please call Johnson Controls to inquire about any updates.
Johnson Controls, Inc., 507 E. Michigan Street, Milwaukee, WI 53202.
Purpose Reference 3 3
vice Data Base Interface
Description 13N2 Physical Characteristics N2 Protocol 13
Transmission Format 13 Defined Messages 15 Message Structures 16
Upload/Download Messages 36 Error Codes Timing Master Slave 41 42 43 40
Polling Mechanism 42
Command Mechanism Error Handling 44
Master Slave 44 44
Buffer Sizing 45
This specification is intended to allow Johnson Controls, Inc. or othercompanies to design N2 devices that can be easily integrated into the Metasys® Network. The N2 protocol is intended to be general in nature, since the actual interface to each device type on the N2 may have some unique properties.
The N2 model hardware device is the virtual object (see Figure 1). The model allows for analog inputs/outputs, binary inputs/outputs, and internal floats/integers/bytes bittypes. The model can have a maximum of 256 of each type. Notes: When the statement “JCI use Only” appears in this document, it means that this byte or message structure is reserved for Johnson Controls use only and should not be used by any vendor device. When the statement “Optional” appears in this document, it means that this message is not required to be implemented by a vendor device for itto considered “Metasys Compatible”. The vendor may still choose to implement the message, however, the N2OPEN compatibility test tool will not check it and no Metasys supervisory system will send the message or expect a response to it for the vendor device type. • Optomux® Operational Manual (Part #1927)
Device Data Base Interface
The N2 System protocol is a general interface for accessingdata that resides in devices on the N2 network. Each device on the N2 can be thought of as a data base manager. The key to referencing a specific N2 device’s data base is the device’s N2 address. The data under the management of a particular N2 device can further be subdivided into groupings called regions. Each region is made up of one or more records, each record within a region having the same...