ISO 16484-5:2022
(Main)Building automation and control systems (BACS) - Part 5: Data communication protocol
Building automation and control systems (BACS) - Part 5: Data communication protocol
The purpose of this document is to define data communication services and protocols for computer equipment used for monitoring and control of HVAC&R and other building systems and to define, in addition, an abstract, object-oriented representation of information communicated between such equipment, thereby facilitating the application and use of digital control technology in buildings.
Systèmes de contrôle et d'automatisation des bâtiments (BACS) — Partie 5: Protocole de communication de données
L'objectif de cette norme est de définir des services et des protocoles de communication de données pour les équipements informatiques utilisés pour la surveillance et le contrôle des systèmes CVC&R et d'autres systèmes de bâtiment et de définir, en outre, une représentation abstraite et orientée objet des informations communiquées entre ces équipements, facilitant ainsi l'application et l'utilisation de la technologie de contrôle numérique dans les bâtiments.
General Information
- Status
- Published
- Publication Date
- 31-Aug-2022
- Technical Committee
- ISO/TC 205 - Building environment design
- Drafting Committee
- ISO/TC 205 - Building environment design
- Current Stage
- 9092 - International Standard to be revised
- Start Date
- 30-Apr-2025
- Completion Date
- 13-Dec-2025
Relations
- Effective Date
- 06-Jun-2022
- Effective Date
- 06-Jun-2022
- Effective Date
- 06-Jun-2022
Overview
ISO 16484-5:2022 - Building automation and control systems (BACS) - Part 5: Data communication protocol - defines the data communication services, protocols and an abstract object‑oriented information model used for monitoring and controlling HVAC&R and other building systems. Published by ISO, this standard specifies the BACnet protocol architecture and the representation of control devices as collections of standardized objects to enable interoperable digital control across building systems.
Key topics and technical requirements
- BACnet protocol architecture: collapsed architecture, network topology and security considerations.
- Application layer: APDU/APDU segmentation, application protocol state machines, time‑sequence diagrams and service conventions for reliable device-to-device services.
- Network layer: service specification, PDU structure, multicast/multiple‑recipient messages, routing behavior and procedures for BACnet routers.
- Data link / physical layers: mappings and requirements for multiple media including Ethernet (ISO 8802-3), ARCNET, MS/TP (Master‑Slave/Token‑Passing), Point‑to‑Point (PTP) and LonTalk. Includes MAC/LLC mappings, physical media parameters, CRC and COBS encoding for serial links.
- Object model: detailed object types and attributes (e.g., Analog Input/Output/Value, Binary Input/Output/Value, Schedule, Trend Log, Device, Access Control, Life Safety, Event Log, Program, Loop and many more). The model defines how device features are exposed and controlled via standardized properties and services.
- Interoperability & implementation guidance: device design choices, routers, half‑routers, repeaters and medium access control procedures to ensure predictable communication behavior.
Practical applications and users
ISO 16484-5 (BACnet) is used to design, specify, implement and integrate building automation systems such as:
- HVAC control, refrigeration and energy management
- Lighting control and scheduling
- Access control and life‑safety integration
- Trend logging, fault detection and analytics
Primary users include:
- Building automation engineers and system integrators
- BACS manufacturers and firmware developers
- Facility managers and commissioning teams
- Consultants, specifiers and test laboratories focused on interoperability and compliance
Related standards
- ISO 16484 series (other Parts of BACS standards) and international IEC/IEEE networking/physical layer standards referenced within (e.g., ISO 8802‑3 for Ethernet).
- Industry protocol family: commonly referred to as BACnet, the de facto data communication protocol for building automation.
ISO 16484-5:2022 is essential for anyone implementing interoperable, object‑oriented building control networks and seeking standardized communication across diverse building systems.
Frequently Asked Questions
ISO 16484-5:2022 is a standard published by the International Organization for Standardization (ISO). Its full title is "Building automation and control systems (BACS) - Part 5: Data communication protocol". This standard covers: The purpose of this document is to define data communication services and protocols for computer equipment used for monitoring and control of HVAC&R and other building systems and to define, in addition, an abstract, object-oriented representation of information communicated between such equipment, thereby facilitating the application and use of digital control technology in buildings.
The purpose of this document is to define data communication services and protocols for computer equipment used for monitoring and control of HVAC&R and other building systems and to define, in addition, an abstract, object-oriented representation of information communicated between such equipment, thereby facilitating the application and use of digital control technology in buildings.
ISO 16484-5:2022 is classified under the following ICS (International Classification for Standards) categories: 35.240.67 - IT applications in building and construction industry; 91.040.01 - Buildings in general. The ICS classification helps identify the subject area and facilitates finding related standards.
ISO 16484-5:2022 has the following relationships with other standards: It is inter standard links to ISO 9957-2:2019, ISO 16484-5:2017/Amd 1:2020, ISO 16484-5:2017. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
You can purchase ISO 16484-5:2022 directly from iTeh Standards. The document is available in PDF format and is delivered instantly after payment. Add the standard to your cart and complete the secure checkout process. iTeh Standards is an authorized distributor of ISO standards.
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 16484-5
Seventh edition
2022-09
Building automation and control
systems (BACS) —
Part 5:
Data communication protocol
Systèmes d'automatisation et de gestion technique du bâtiment —
Partie 5: Protocole de communication de données
Reference number
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
CONTENTS Page
FOREWORD . xii
1 PURPOSE . 1
2 SCOPE . 1
3 DEFINITIONS . 1
3.1 Terms Adopted from International Standards . 1
3.2 Terms Defined for this Standard . 3
3.3 Abbreviations and Acronyms Used in this Standard . 7
4 BACnet PROTOCOL ARCHITECTURE . 11
4.1 The BACnet Collapsed Architecture . 12
4.2 BACnet Network Topology . 14
4.3 Security . 14
5 THE APPLICATION LAYER . 16
5.1 The Application Layer Model . 16
5.2 Segmentation of BACnet Messages . 20
5.3 Transmission of BACnet APDUs . 21
5.4 Application Protocol State Machines . 25
5.5 Application Protocol Time Sequence Diagrams . 41
5.6 Application Layer Service Conventions . 50
6 THE NETWORK LAYER . 52
6.1 Network Layer Service Specification . 52
6.2 Network Layer PDU Structure . 54
6.3 Messages for Multiple Recipients . 59
6.4 Network Layer Protocol Messages . 60
6.5 Network Layer Procedures . 64
6.6 BACnet Routers . 66
6.7 Point-To-Point Half-Routers . 71
7 DATA LINK/PHYSICAL LAYERS: Ethernet (ISO 8802-3) LAN . 76
7.1 The Use of ISO 8802-2 Logical Link Control (LLC) . 76
7.2 Parameters Required by the LLC Primitives . 76
7.3 Parameters Required by the MAC Primitives . 76
7.4 Physical Media . 76
8 DATA LINK/PHYSICAL LAYERS: ARCNET (ATA 878.1) LAN . 77
8.1 The Use of ISO 8802-2 Logical Link Control (LLC) . 77
8.2 Parameters Required by the LLC Primitives . 77
8.3 Mapping the LLC Services to the ARCNET MAC Layer . 77
8.4 Parameters Required by the MAC Primitives . 77
8.5 Physical Media . 77
9 DATA LINK/PHYSICAL LAYERS: MASTER-SLAVE/TOKEN-PASSING (MS/TP) LAN . 79
9.1 Service Specification . 79
9.2 Physical Layer . 81
9.3 MS/TP Frame Format . 90
9.4 Overview of the MS/TP Network . 92
9.5 MS/TP Medium Access Control . 92
9.6 Cyclic Redundancy Check (CRC) . 111
9.7 Interfacing MS/TP LANs with Other BACnet LANs . 112
9.8 Responding BACnet User Processing of Messages from MS/TP . 112
9.9 Repeaters . 113
9.10 COBS (Consistent Overhead Byte Stuffing) Encoding . 114
9.11 Documenting MS/TP Device Design Choices . 118
10 DATA LINK/PHYSICAL LAYERS: POINT-TO-POINT (PTP) . 119
10.1 Overview . 119
10.2 Service Specification . 119
10.3 Point-to-Point Frame Format . 124
10.4 PTP Medium Access Control Protocol . 126
11 DATA LINK/PHYSICAL LAYERS: LonTalk (ISO/IEC 14908.1) LAN . 147
11.1 The Use of ISO 8802-2 Logical Link Control (LLC) . 147
11.2 Parameters Required by the LLC Primitives . 147
11.3 Mapping the LLC Services to the LonTalk Application Layer . 147
11.4 Parameters Required by the Application Layer Primitives . 147
11.5 Physical Media . 148
12 MODELING CONTROL DEVICES AS A COLLECTION OF OBJECTS . 149
12.1 Object Characteristics and Requirements . 149
12.2 Analog Input Object Type . 155
12.3 Analog Output Object Type . 162
12.4 Analog Value Object Type . 169
12.5 Averaging Object Type . 177
12.6 Binary Input Object Type . 181
12.7 Binary Output Object Type. 188
12.8 Binary Value Object Type . 197
12.9 Calendar Object Type . 205
12.10 Command Object Type . 208
12.11 Device Object Type . 214
12.12 Event Enrollment Object Type . 226
12.13 File Object Type. 234
12.14 Group Object Type . 238
12.15 Life Safety Point Object Type . 241
12.16 Life Safety Zone Object Type . 248
12.17 Loop Object Type . 255
12.18 Multi-state Input Object Type . 265
12.19 Multi-state Output Object Type . 271
12.20 Multi-state Value Object Type . 278
12.21 Notification Class Object Type . 285
12.22 Program Object Type . 291
12.23 Pulse Converter Object Type . 298
12.24 Schedule Object Type . 306
12.25 Trend Log Object Type . 313
12.26 Access Door Object Type . 323
12.27 Event Log Object Type . 332
12.28 Load Control Object Type . 340
12.29 Structured View Object Type . 350
12.30 Trend Log Multiple Object Type . 355
12.31 Access Point Object Type . 365
12.32 Access Zone Object Type . 382
12.33 Access User Object Type . 390
12.34 Access Rights Object Type . 394
12.35 Access Credential Object Type . 400
12.36 Credential Data Input Object Type . 410
12.37 CharacterString Value Object Type . 416
12.38 DateTime Value Object Type . 423
12.39 Large Analog Value Object Type . 429
12.40 BitString Value Object Type . 437
12.41 OctetString Value Object Type . 444
12.42 Time Value Object Type . 448
12.43 Integer Value Object Type . 454
12.44 Positive Integer Value Object Type . 462
12.45 Date Value Object Type . 470
12.46 DateTime Pattern Value Object Type . 476
12.47 Time Pattern Value Object Type . 482
12.48 Date Pattern Value Object Type . 488
12.49 Deleted Clause . 494
12.50 Global Group Object Type . 495
12.51 Notification Forwarder Object Type . 502
12.52 Alert Enrollment Object Type . 510
12.53 Channel Object Type . 514
12.54 Lighting Output Object Type . 524
12.55 Binary Lighting Output Object Type . 539
12.56 Network Port Object Type . 549
iv © ISO 2022 – All rights reserved
12.57 Timer Object Type . 573
12.58 Elevator Group Object Type . 585
12.59 Lift Object Type . 589
12.60 Escalator Object Type . 601
12.61 Accumulator Object Type . 608
12.62 Staging Object Type . 618
12.63 Audit Reporter Object Type . 628
12.64 Audit Log Object Type . 633
13 ALARM AND EVENT SERVICES . 640
13.1 Change of Value Reporting . 640
13.2 Event Reporting . 645
13.3 Event Algorithms . 656
13.4 Fault Algorithms . 685
13.5 AcknowledgeAlarm Service . 692
13.6 ConfirmedCOVNotification Service . 694
13.7 UnconfirmedCOVNotification Service . 696
13.8 ConfirmedEventNotification Service . 697
13.9 UnconfirmedEventNotification Service . 700
13.10 GetAlarmSummary Service . 703
13.11 GetEnrollmentSummary Service . 705
13.12 GetEventInformation Service . 708
13.13 LifeSafetyOperation Service . 710
13.14 SubscribeCOV Service . 712
13.15 SubscribeCOVProperty Service . 715
13.16 SubscribeCOVPropertyMultiple Service . 718
13.17 ConfirmedCOVNotificationMultiple Service. 723
13.18 UnconfirmedCOVNotificationMultiple Service . 726
13.19 AuditLogQuery . 728
13.20 ConfirmedAuditNotification . 732
13.21 UnconfirmedAuditNotification . 733
14 FILE ACCESS SERVICES . 734
14.1 AtomicReadFile Service . 734
14.2 AtomicWriteFile Service . 737
15 OBJECT ACCESS SERVICES . 740
15.1 AddListElement Service . 740
15.2 RemoveListElement Service . 742
15.3 CreateObject Service . 744
15.4 DeleteObject Service . 747
15.5 ReadProperty Service . 748
15.6 Deleted Clause . 750
15.7 ReadPropertyMultiple Service . 751
15.8 ReadRange Service . 754
15.9 WriteProperty Service . 762
15.10 WritePropertyMultiple Service . 764
15.11 WriteGroup Service . 767
16 REMOTE DEVICE MANAGEMENT SERVICES. 769
16.1 DeviceCommunicationControl Service . 769
16.2 ConfirmedPrivateTransfer Service. 771
16.3 UnconfirmedPrivateTransfer Service . 773
16.4 ReinitializeDevice Service . 774
16.5 ConfirmedTextMessage Service. 776
16.6 UnconfirmedTextMessage Service . 778
16.7 TimeSynchronization Service . 779
16.8 UTCTimeSynchronization Service . 780
16.9 Who-Has and I-Have Services . 781
16.10 Who-Is and I-Am Services . 783
16.11 Who-Am-I and You-Are Services . 785
17 VIRTUAL TERMINAL SERVICES . 787
17.1 Virtual Terminal Model . 787
17.2 VT-Open Service . 791
17.3 VT-Close Service . 793
17.4 VT-Data Service . 794
17.5 Default Terminal Characteristics . 796
18 ERROR, REJECT, and ABORT CODES . 800
18.1 Error Class - DEVICE . 800
18.2 Error Class - OBJECT . 800
18.3 Error Class - PROPERTY . 801
18.4 Error Class - RESOURCES . 802
18.5 Error Class - SECURITY . 803
18.6 Error Class - SERVICES . 804
18.7 Error Class - COMMUNICATION . 805
18.8 Error Class - VT . 809
18.9 Reject Reason . 810
18.10 Abort Reason . 810
18.11 Confirmed Service Common Errors . 811
19 BACnet PROCEDURES . 812
19.1 Backup and Restore. 812
19.2 Command Prioritization . 817
19.3 Device Restart Procedure . 822
19.4 Determining Maximum Conveyable APDU . 823
19.5 Value Source Mechanism . 825
19.6 Audit Logging . 827
19.7 Unconfigured Device Discovery and Address Assignment . 838
20 ENCODING BACnet PROTOCOL DATA UNITS . 839
20.1 Encoding the Fixed Part of BACnet APDUs . 840
20.2 Encoding the Variable Part of BACnet APDUs . 851
21 FORMAL DESCRIPTION OF APPLICATION PROTOCOL DATA UNITS . 866
21.1 APDU Definitions . 866
21.2 Confirmed Service Productions . 868
21.3 Unconfirmed Service Productions . 878
21.4 Error Productions . 881
21.5 Application Types . 891
21.6 Base Types . 892
22 CONFORMANCE AND INTEROPERABILITY . 960
22.1 Conformance to BACnet . 960
22.2 BACnet Interoperability . 961
23 EXTENDING BACnet TO ACCOMMODATE VENDOR PROPRIETARY INFORMATION . 963
23.1 Extending Enumeration Values. 963
23.2 Using the PrivateTransfer Services to Invoke Non-Standardized Services . 964
23.3 Adding Proprietary Properties to a Standardized Object . 964
23.4 Adding Proprietary Object Types to BACnet. 965
23.5 Restrictions on Extending BACnet . 965
24 DELETED CLAUSE . 966
25 REFERENCES. 967
ANNEX A - PROTOCOL IMPLEMENTATION CONFORMANCE STATEMENT (NORMATIVE) . 971
ANNEX B - GUIDE TO SPECIFYING BACnet DEVICES (INFORMATIVE). 974
ANNEX C - Removed . 975
ANNEX D
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