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HART Communication Foundation Document Number: HCF_SPEC-081
Document Title: Token-Passing Data Link Layer Specification
Revision 9.0, Release Date: 12 May 2012 Page 13 of 65
The following are RS-485 related documentation:
HART RS-485 Physical Layer Implementation Definition. Rosemount Inc. 19 March, 1992
Electrical Characteristics of Generators and Receivers for Use in Balanced Digital Multipoint Systems.
ANSI/EIA/TIA RS-485. Electronic Industry Alliance. 1982
The following are Infrared related documentation:
[IRPHY] Infrared Data Association Serial Infrared Physical Layer Specification Version 1.4, Infrared
Data Association, 2001
The following reference describes the methods for specifying state transition diagrams used in this document .
[Hatley] Hatley, D., and Pirbhai, I. Strategies for Real-Time System Specification. Dorset House,
1987.
3. DEFINITIONS
Definitions for terms can be found in HART Field Communications Protocol Specification. Terms used in this
document include: Broadcast Address, Burst Mode, Burst Mode Device, Data Link Layer, Master, Multi-drop,
Preamble, Response Message, Slave, Slave Time-Out, Software Revision Level, Time Constant, Units Code
Some of the following definitions are included in the HART Field Communications Protocol Specification .
However, these definitions are critical to the understanding of this specification. As a result, they are included
and their meaning amplified. Three types of network connections are used throughout this specification to
completely define the HART Data Link Layer requirements.
Burst-Mode Device
This is a device which provides a digital response carrying measurement or other
data, at regular intervals, without the data being specifically requested, i.e., this
device normally functions as an independently broadcasting device. A Burst-
Mode Device is defined to be a Slave Device with burst mode capability (hence
the use of the word "mode" in describing the device type). When such a mode is
enabled, the Slave Device is said to "be in burst mode".
Field Device
A Slave or Burst-Mode Device.
Master Device
A Master Device is responsible for initiating, controlling and terminating
transactions with a slave device or a burst mode device. A distinction is made
between master devices into Primary Masters and Secondary Masters in order to
allow the simultaneous use of two Master Devices on a HART communication
link. The same protocol rules are followed by a Primary Master and a Secondary
Master except for customizing time-outs that differentiate between them.
Slave Device
This is a device which accepts or provides a digital message carrying
measurement or other data, but only when specifically requested, i.e., this device
always functions as a slave in a master/slave relationship.
Time Sequence Diagram
A diagram used to illustrate the interrelationship between the Protocol services.
The protocol layer of interest and the lower, intervening layers are treated as a
"black box". The internal workings of these layers are not shown on this diagram.
The time sequence diagram shows the interactions between the service
primitives over time.
Sometimes referred to as a Message Sequence Diagram.
Unique Identifier
The concatenation of the Expanded Device Type and Device ID. Every field
device manufactured with a given Expanded Device Type must have a different
Device ID. A subset of the Unique Identifier is used in the Long Frame Address.