HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

S T A N

D A R D

HART Communication Protocol Specification

HCF_SPEC-13, Revision 7.2 Release Date: 9 March, 2009

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13

HART Communication Protocol Specification

Release Date: 9 March, 2009

Document Distribution / Maintenance Control / Document Approval

To obtain information concerning document distribution control, maintenance control, and document approval please contact the HART Communication Foundation (HCF) at the address shown below. Copyright © 1993 (1995 – 1999, 2001, 2004 –2009) HART® Communication Foundation

This document contains copyrighted material and may not be reproduced in any fashion without the written permission of the HART Communication Foundation.

Trademark Information

HART® is a registered trademark of the HART Communication Foundation, Austin, Texas, USA. Any use of the term HART hereafter in this document, or in any document referenced by this document, implies the registered trademark. WirelessHART™ is a trademark of the HART Communication Foundation. All other trademarks used in this or referenced documents are trademarks of their respective companies. For more information contact the HCF Staff at the address below.

Attention: Foundation Director

HART Communication Foundation

9390 Research Boulevard

Suite I-350

Austin, TX 78759, USA

Voice: (512) 794-0369

FAX: (512) 794-3904

http://

Intellectual Property Rights

The HCF does not knowingly use or incorporate any information or data into the HART Protocol Standards which the HCF does not own or have lawful rights to use. Should the HCF receive any notification regarding the existence of any conflicting Private IPR, the HCF will review the disclosure and either (a) determine there is no conflict; (b) resolve the conflict with the IPR owner; or (c) modify the standard to remove the conflicting requirement. In no case does the HCF encourage implementers to infringe on any individual's or organization's IPR.

Revision 7.2, Release Date: 9 March, 2009 Page 2 of 35

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13

HART Communication Protocol Specification

Table of Contents

Preface (5)

Introduction (7)

1.Scope (9)

1.1Conformance Requirements (9)

1.2Terms and Conditions (9)

2.References (11)

2.1The HART Communication Protocol Specification (11)

2.2Related HART Documents (12)

2.3Related Communication Documents (12)

3.Definitions (12)

4.Protocol Revision Rules (20)

4.1Specification Identification (20)

4.2HART Communication Protocol Revision Level (21)

4.3Modifications to Protocol Specifications (22)

4.4Approval (23)

5.HART Communication Protocol Revision Matrix (23)

6.HART Communication Protocol Document List (26)

Annex A.Revision History (32)

A1.Changes from Revision 7.1 to 7.2 (32)

A2.Changes from Revision 7.0 to 7.1 (32)

A3.Changes from Revision 6.5 to 7.0 (32)

A4.Changes from Revision 6.4 to 6.5 (32)

A5.Changes from Revision 6.3 to 6.4 (33)

A6.Changes from Revision 6.2 to 6.3 (33)

A7.Changes from Revision 6.1 to 6.2 (33)

A8.Changes from Revision 6.0 to 6.1 (33)

A9.Changes from Revision 5.9 to 6.0 (34)

A10.Changes from Revision 5.8 to 5.9 (34)

A11.Changes from Revision 5.7 to 5.8 (34)

A12.Changes from Revision 5.6 to 5.7 (35)

Revision 7.2, Release Date: 9 March, 2009 Page 3 of 35

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13

HART Communication Protocol Specification

List of Tables

Table 1. HART Protocol Specification Revision 7.1 Documents (11)

Table 2. HART Protocol Revision Number Cross Reference (24)

Table 3. HART Communication Protocol Specification (26)

Table 4. Physical and Data Link Layer Specification (27)

Table 5. FSK Physical Layer Specification (27)

Table 6. C8PSK Physical Layer Specification (27)

Table 7. 2.4GHz DSSS O-QPSK Physical Layer Specification (27)

Table 8. Voltage Modulation Physical Layer Specification (27)

Table 9. TDMA Data-Link Layer (28)

Table 10. Token-Passing Data Link Layer Specification (28)

Table 11. Network Management Specification (28)

Table 12. Command Summary Specification (28)

Table 13. Universal Command Specification (29)

Table 14. Common Practice Command Specification (29)

Table 15. Wireless Command Specification (30)

Table 16. Device Families Command Specification (30)

Table 17. Common Tables Specification (30)

Table 18. Block Transfer Specification (31)

Table 19. Discrete Applications Specification (31)

Table 20. Wireless Devices Specification (31)

Table 21. Command Response Code Specification (31)

Revision 7.2, Release Date: 9 March, 2009 Page 4 of 35

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13

HART Communication Protocol Specification

Preface

This preface is included for informational purposes only.

Since release of the HART Communication Protocol Revision 7.0 Specifications in September 2007, HCF staff and Technical Working Groups updating existing HART Test Specifications and developing new Test Specifications for wireless have closely scrutinized the Protocol Specifications. Any anomalies, errors or inadvertent omissions discovered in the Specifications have been identified, tracked and resolved.

HART Protocol Revision 7.1 includes all changes, clarifications and corrections resolved during the process with corrections and clarifications documented in Addendums to each of the following specifications:

•TDMA Data-Link Layer Specification (HCF_SPEC-075)

•Network Management Specification (HCF_SPEC-085)

•Universal Command Specification (HCF_SPEC-127)

•Common Practice Command Specification (HCF_SPEC-151)

•Wireless Command Specification (HCF_SPEC-155)

•Wireless Devices Specification (HCF_SPEC-290)

HART Protocol Revision 7.1 provides developers with the most current, accurate and up-to-date information on the HART 7 Specifications. The Addendums clearly describe each correction or clarification by Specification subsection and brief explanation of the change. All changes described in the Specification Addendums are mandatory.

Corrections and clarifications in this revision address the following areas:

•TDMA Data-Link Layer state machines

•The RSL averaging algorithm.

•Enumeration of Null and default values.

•Operation of bandwidth management services including:

•Network Management Service Primitives (SP)

•Response Codes in Commands 799-801 and 973

•During the join process.

•When publishing process data and performing block data transfers.

•Wireless peer-to-peer communications

Revision 7.2, Release Date: 9 March, 2009 Page 5 of 35

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13

HART Communication Protocol Specification

•Nonce counter history.

•Network Layer state machines.

•Burst messaging of 16-bit Commands.

•Mandatory and recommended command support listed by device type

•Response Codes in certain Wireless commands

•Statistics found in Commands 779, 780, and 840

In addition, HART Protocol Revision 7.1 includes an update to the Common Tables Specification (HCF_SPEC-183). As per HCF standard practice, the Common Tables Specification is periodically updated and released to add new Manufacturer ID, Expanded Device Type Codes and other necessary table enumerations. The cover page and copyright / trademark information page of each specification document has also been updated with the new HART Logo.

Revision 7.2, Release Date: 9 March, 2009 Page 6 of 35

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13 HART Communication Protocol Specification

Revision 7.2, Release Date: 9 March, 2009

Page 7 of 35

Introduction

This introduction is included for informational purposes only.

Designed to compliment traditional 4-20mA analog signaling, the HART Protocol supports two way digital communications for process measurement and control devices. Applications include remote process variable interrogation, cyclical access to process data, parameter setting and diagnostics. This document defines the specification documents that comprise the HART Communication Protocol. Specification of the HART protocol is based largely on the OSI 7-Layer Communication

Model (see Figure 1).

Wired FSK/PSK & RS485WIreless 2.4GHz

OSI Layer Function

HART

Figure 1. OSI 7-Layer Model

The HART protocol specifications directly address 5 layers in the OSI model: the Application, Transport, Network, Data-Link and Physical Layers.

The HART Application Layer is extensive and plays a major role in ensuring the interoperability of devices from different companies. The Application Layer defines the commands, responses, data types and status reporting supported by the Protocol. The Command Summary (HCF_SPEC-099), Common Tables (HCF_SPEC-183) and Command Response Code (HCF_SPEC-307) Specifications establish mandatory Application Layer practices (e.g. data types, common definitions of data items, and procedures). The Universal Command Specification (HCF_SPEC-127) specifies the minimum Application Layer content for all HART compatible devices.

The Application Layer also standardizes optional capabilities. The Common Practice Command Specification (HCF_SPEC-151) defines many (optional) commands useful to a broad range of devices. The Device Families Specification (HCF_SPEC-190) further standardizes commands, status alerts and procedures for various types of devices based on the device’s primary function, sensor technology and/or process application.

The popularity of HART Communication has also stimulated industry demands for expanding application of the HART protocol into new domains beyond continuous measurement and control

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13

HART Communication Protocol Specification

type devices. The Discrete Applications Specification (HCF_SPEC-285 - still under development) responds to industry demands for defining application of the HART Protocol to smart discrete (on-off) type devices.

The synergy between HART Communication and the low power, short message requirements for wireless sensor applications have also led to wireless capabilities being added to the HART Protocol. This exciting new capability known as WirelessHART™ expands the possibilities and opens the door to new opportunities for both end users and suppliers in process automation. WirelessHART™ - the new interoperable wireless communication standard for process measurement and control device applications.

WirelessHART establishes the wireless communication standard for process applications. WirelessHART further extends the application of HART Communications and the benefits it provides to industry by enhancing the HART Technology to support wireless process automation applications while meeting the following goals:

•Preserve and enhance industry's existing investment in HART Technology.

•Leverage proven, established technologies, standards, and practices wireless communication.

•Maximize coexistence by ensuring reliable WirelessHART communications while minimizing interference to other wireless technologies.

WirelessHART is an optional HART Physical Layer that provides a low cost, wireless connection to HART-enabled field devices. The principal objectives of WirelessHART includes: •Compatibility with existing HART Application Layer

•Leverage existing host applications and the large installed base

•Must be HART-like: simple, reliable, easy-to-use, high-value

•Supply end-users with new capabilities

•Provide more flexibility for installing and operating process instrumentation and controls WirelessHART is very interoperable and allows compliant devices from different manufactures to be mixed to create an integrated, functioning system.

Revision 7.2, Release Date: 9 March, 2009 Page 8 of 35

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13

HART Communication Protocol Specification

1.SCOPE

This document identifies the revision level of the HART Communication Protocol; phrases commonly used throughout the Protocol; and the documents that comprise the HART Protocol Specification. Any product claiming compliance with the HART Protocol must meet all specifications defined by this document and the indicated revision level of the specification documents included by reference. Referenced documents define the different elements of the protocol (i.e., Data Link Layer, Physical Layer, and Application Layer).

In addition, this document defines the mechanisms for identifying the HART Communication Protocol Specification, the revision level of the specification and approval of changes to the specification.

1.1Conformance Requirements

HART protocol revisions include many different specifications all of which are designed to work together as set. Mixing specifications from different Protocol revisions is not allowed. Any product claiming compliance with the HART Protocol must adhere to all specifications in a specific HART Protocol revision. New and revised HART field device implementations should use the latest HART Protocol revision.

Devices claiming HART Protocol compliance must adhere to all HART Protocol specifications including the device type and device revision numbering. Device types and device revision numbers must be assigned as specified in the Command Summary Specification and Token-Passing Data Link Layer Specification.

Devices claiming HART Protocol compliance must comply with the requirements in the Token-Passing Data Link Layer Specification and support at least one of the Physical Layers that it specifies.

Manufacturers' Device-Specific Documents (see Section 2.2) are not formally part of the HART Protocol Specifications. While these documents are developed and controlled by the respective device manufacturer, they must comply with the Device-Specific Command revision criteria found in the Command Summary Specification.

1.2Terms and Conditions

Subject to the Terms and Conditions of this Agreement, the HART Communication Foundation (the "HCF") grants You (the "User") a non-exclusive, limited license to use the HART Communication Protocol Specification and related materials (collectively, the "HART Materials") furnished hereunder to make, use, sell or distribute products complying with the standards included in the HART Materials. The HCF holds and retains all worldwide rights, title and interests, including without limitation, copyright in and to all HART Materials.

Revision 7.2, Release Date: 9 March, 2009 Page 9 of 35

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13

HART Communication Protocol Specification

1.2.1Warranty and Liability Disclaimers

User expressly acknowledges and agrees that HCF is providing the HART Materials "AS IS" AND WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, WARRANTIES OF PERFORMANCE, MECHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE.

User also expressly acknowledges and agrees that USER BEARS ALL RISKS FOR USE OF HART MATERIALS AND UNDER NO CIRCUMSTANCES, INCLUDING NEGLIGENCE, SHALL HCF BE LIABLE FOR ANY COSTS, EXPENSES, LOSSES, OR DAMAGES, INCLUDING BUT NOT LIMITED TO, DIRECT, INDIRECT, CONSEQUENTIAL, INCIDENTAL, SPECIAL OR OTHER DAMAGES IN TORT, CONTRACT, PRODUCT LIABILITY OR UNDER ANY OTHER THEORY OF LAW RESULTING FROM ANY USE OF THE HART MATERIALS.

1.2.2General Provisions

This Agreement is effective until terminated by either party and will terminate independently without notice if User fails to comply with any provision of the Agreement or any instructions provided by HCF regarding HART Materials. Upon termination for any reason, User must cease all use of HART Materials and return all HART Materials provided to User by HCF with all copies thereof.

This Agreement shall be governed and construed in accordance with the laws of United States and the State of Texas. If for any reason a court of competent jurisdiction finds any provision of this Agreement, or a portion thereof, to be unenforceable, that provision shall be enforced to the maximum extent permissible to affect the intent of the parties and all other provisions shall remain in full force and effect.

This Agreement constitutes the entire agreement between User and HCF with respect to all HART Materials provided to User by HCF and supersedes any prior understanding or agreement (oral or written) regarding HART Materials. HCF may modify this agreement at any time for any reason. Revision 7.2, Release Date: 9 March, 2009 Page 10 of 35

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13 HART Communication Protocol Specification

Revision 7.2, Release Date: 9 March, 2009 Page 11 of 35 2. REFERENCES

2.1 The HART Communication Protocol Specification

The HART Communication Protocol Specification is a set of documents that define the HART

Communication Protocol. This version of the specification is defined by the documents identified in

Table 1. Table 1. HART Protocol Specification Revision 7.2 Documents

Document Title Doc. Rev. Doc.

Number

HART Communication Protocol Specification 7.2 HCF_SPEC-13

FSK Physical Layer Specification

8.1 HCF_SPEC-54 C8PSK Physical Layer Specification 1.0 HCF_SPEC-60 2.4GHz DSSS O-QPSK Physical Layer Specification

1.0 HCF_SPEC-065 TDMA Data-Link Layer

1.1 HCF_SPEC-075 Token-Passing Data Link Layer Specification 8.2 HCF_SPEC-81

Network Management Specification 1.2 HCF_SPEC-085 Command Summary Specification 9.0 HCF_SPEC-99 Universal Command Specification 7.1 HCF_SPEC-127 Common Practice Command Specification 9.1 HCF_SPEC-151 Wireless Command Specification

1.1 HCF_SPEC-155 Device Families Command Specification. 1.0 HCF_SPEC-160

Common Tables Specification 20.0 HCF_SPEC-183 Block Data Transfer Specification 1.0 HCF_SPEC-190 Discrete Applications Specification 1.0 HCF_SPEC-285

Wireless Devices Specification 1.1 HCF_SPEC-290 Command Response Code Specification 6.0 HCF_SPEC-307

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13

HART Communication Protocol Specification

2.2Related HART Documents

The Protocol Specifications frequently reference the manufacturers' device-specific document. Device-specific documents are developed and controlled by the respective manufacturer and should follow the requirements of the following HART Communication Foundation document: Requirements for Device-Specific Documentation. HCF_LIT-18

2.3Related Communication Documents

ANSI X3.4-1983. Code for Information Interchange (ASCII).

ISO 7498-1984. Open Systems Interconnection – Basic Reference Model.

ISO 646. Information Processing – ISO 7-bit coded character set for information

interchange.

ISO 8859-1-1987. Information Processing –8-bit single-byte coded graphic character sets.

Part 1 Latin alphabet No. 1.

IEEE 754. Standard for Binary Floating-Point Arithmetic.

3.DEFINITIONS

Definitions of standard terms used throughout the Protocol Specifications are included here as a reference. All specification documents use these terms as defined below. However, individual Specification documents may define terms that are unique to that document as long as they do not conflict with the following definitions:

ACK Message type 0x06. A Slave acknowledge to the Master's STX.

See the Data Link Layer Specification for more information. Actuator A field device whose primary purpose is to vary its output thus

affecting the connected process. An actuator typically uses the

analog 4-20mA Loop Current as a setpoint.

Analog Channel A continuously variable electrical signal connecting a field device

to the remainder of the data acquisition or control system. Some

field devices support multiple analog channels (input or output).

Each Analog Channel transmits a single Dynamic Variable to or

from the field device.

Application Layer Topmost layer in the Open System Interconnect (OSI) model. In

the HART Protocol this layer includes: the definitions of data types;

revision rules; application procedures; and the HART Commands. Revision 7.2, Release Date: 9 March, 2009 Page 12 of 35

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13 HART Communication Protocol Specification

Revision 7.2, Release Date: 9 March, 2009 Page 13 of 35 ASCII ASCII (American Standard Code for Information Interchange) is a

character code defined by ANSI (the American National Standards Institute). It represents the U.S alphabet (upper and lower case), numbers 0 to 9, and many punctuation characters as 7-bit binary codes. A number of codes are allocated for control functions such as start of text, end of text, carriage return, tab, and backspace.

Many HART commands use a 6-bit subset of ASCII (see Packed ASCII ). In most cases HART uses ASCII interchangeably with ISO Latin-1.

BACK

Message type 0x01. A Slave Burst message. See the Data Link Layer Specification for more information. Bridge Device A device that acts as a bridge between the HART network and

another network. The other network could be another HART network.

Broadcast Address A broadcast address is used by a master to send a command to all devices on the loop. However, only a single slave responds to the command. The slave must use other means (e.g. parameters in the data field) to determine if it responds to the command. The Broadcast Address is 38 bits of zeros in place of the Unique Identifier in the long frame address.

Burst Mode A special mode of a slave device which repeatedly sends the response to a selected HART command without the need for a request from a master.

Burst Mode Device A slave device that repeatedly issues the reply to a selected command. Once a slave is in this (optional) mode, the reply is sent without any further action by any master. A bursting slave is like a tertiary master because it also initiates channel activity.

Busy The device is busy and cannot execute this command at this time. A device indicates Busy by returning Response Code 32 when allowed by the command specification. The requested command is not executed if a Busy response is returned.

Data Field The sixth field in a HART message. The length of the Data field is indicated by the Byte Count field. The Data field contains the Application Layer content and is divided into sub-fields (See the Command Summary Specification ).

Data Link Layer

Layer 2 in the OSI model. This layer is responsible for the error-free communication of data. The Data Link Layer defines the message structure, error detection strategy and bus arbitration rules.

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13 HART Communication Protocol Specification

Revision 7.2, Release Date: 9 March, 2009 Page 14 of 35 Delayed Response Allows the slave device to release the communication link (pass the

token) while continuing to execute a command. If a slave is unable to respond to a command within the Slave Time-Out period, a Delayed Response (DR) sequence should be initiated. The DR begins with the slave notifying the master during Slave Time-Out that it is unable to complete the command but will continue the command's execution. Later, the master reissues exactly the same command request to complete the DR. This is quite different from returning a Busy response. See the Co mmand Summary Specification for more information.

The command specification will indicate if a delayed response is allowed for the command.

Delayed Response

Mechanism

See Delayed Response . This mechanism allows a slave to defer the completion of a command, thus allowing more processing time than the Data Link Layer grants a slave. See the Co mmand Summary Specification for more information.

The command specification will indicate if a delayed response is allowed for the command.

Device

A HART compatible Slave or Master. Device ID The integer returned in bytes 9-11 of Identity Commands (see the

Command Summary Specification ). This number is different for every device manufactured with a given Device Type.

Device Reset A hard reset of the device. This is equivalent to a cycling the power off and then back on to the device.

Device Revision The integer returned in byte 5 of Identity Commands (see the Command Summary Specification ). This defines the revision level of the command set supported by the field device including the device-specific commands.

The Command Summary Specification defines when a new Device Type number must be allocated (as opposed to the Device Revision being incremented).

Device Type The integer returned in bytes 1-2 of Identity Commands (see the

Command Summary Specification ). This defines the command set supported by a device.

The Command Summary Specification defines when a new Device Type number must be assigned (as opposed to the Device Revision being incremented). Device Type codes are controlled and must be allocated by the HART Communication Foundation.

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13 HART Communication Protocol Specification

Revision 7.2, Release Date: 9 March, 2009 Page 15 of 35 Device Variable A uniquely defined data item within a Field Device that is always

associated with cyclical process information. A Device Variable's value varies in response to changes and variations in the process. All HART compatible field devices contain Device Variables. However, simple field devices may use only Dynamic Variables and not expose the underlying Device Variables at the Protocol Application Layer interface.

DR_CONFLICT

Delayed Response – Conflict

The requested command would cause a conflict with a currently executing delayed response command. See the Co mmand Summary Specification for more information. DR_DEAD Delayed Response – Dead.

This is only valid for intelligent I/O devices. The host is informed that the slave did not reply to the request. See the Co mmand Summary Specification for more information.

DR_INITIATE Delayed Response – Initiate.

The command could not be serviced in the time given by the Data Link Layer. A Delayed Response was initiated. See the Co mmand Summary Specification for more information.

DR_RUNNING Delayed Response – Running.

The execution of the Delayed Response is not yet finished. The process is still running. See the Co mmand Summary Specification for more information.

Dynamic Variable The connection between the process and an analog channel. All

HART field devices may contain Primary, Secondary, Tertiary, and Quaternary Variables that are mapped to the first 4 analog channels in a field device. These are collectively called the Dynamic Variables. The Primary Variable is always supported and is connected to the first 4-20mA channel, the same channel that always supports HART communication. The SV, TV, and QV may or may not be supported and, furthermore, may not have an associated Analog Channel.

Enumeration

A numerical list where each number corresponds to a specific function or text string. Basically and enumeration is a look-up table (e.g., of engineering unit codes) with each row containing a number and the corresponding function of text string. Extended Command

Number

A 16 bit command number transmitted in the HART Data field. Messages containing an Extended Command Number contain the number 31 in the normal HART Command field.

HART Field Communication Protocol Specification HCF_SPEC-13_spec013.r7.2

HART Communication Foundation Document Number: HCF_SPEC-13 HART Communication Protocol Specification

Revision 7.2, Release Date: 9 March, 2009 Page 16 of 35 Field Device Field Devices are connected to the Process and their Device

Variables vary as process conditions change. From a Data Link Layer perspective, HART compatible Field Devices are either a Slave or Burst Mode Device .

Fixed Current Mode In this mode the field device's Loop Current value is fixed to the value issued by the master. For transmitters, this causes the first analog output to be forced to a fixed value. For actuators, the input loop current value measured by the actuator is set to a fixed value. Floating Point

Floating point represents a real number consisting of an exponent, and a mantissa. HART requires floating point numbers and calculations to conform to the IEEE 754 standard. The HART Protocol uses this representation for many data items including all Dynamic and Device Variables. Generic Host

Generic Master

A host meeting the requirements of, at least, Host Conformance Class 3 (see the Command Summary Specification ) HART Message The fundamental content transmitted across a HART Physical

Layer. The HART Message consists of the following fields: Delimiter, Address, Expansion, Command, Byte Count, Data, and Check Byte. The Expansion and Data fields are not found in all HART Messages. The Data Link Layer Specification explains the construction and framing of HART Messages.

Host One of (possibly) several applications that can be executed sequentially or simultaneously on a Master.

IEEE 754 A standard established by the Institute of Electrical and Electronic Engineers governing floating point number formats and calculations. See Floating Point.

ISO Latin-1 A character code set defined by the International Standards Organization. It represents the U.S and Western European alphabet (upper and lower case), numbers 0 to 9, and many punctuation characters as an 8-bit binary codes. A number of codes are allocated for control functions such as start of text, end of text, carriage return, tab, and backspace.

ISO Latin-1 is an extension of ACSII using the eighth bit to add 127 special Western European characters.

Long Frame

A HART message with a 5 byte address field. All HART commands must support Long Frame messages. See Short Frame . Long Tag A 32 character ISO Latin-1 string used to identify the field device.

See Tag .