Highway Addressable Remote Transducer Protocol: Difference between revisions

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{{Short description|Industrial automation protocol}}

{{Infobox fieldbus protocol

| Name = HART

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The '''HART Communication Protocol (Highway Addressable Remote Transducer)''' is a hybrid analog+digital industrial automation open protocol. Its most notable advantage is that it can communicate over legacy 4–20 mA analog instrumentation current loops, sharing the pair of wires used by the analog-only host systems. HART is widely used in process and instrumentation systems ranging from small automation applications up to highly sophisticated industrial applications.

HARTBased is a inon the [[OSI model]], HART resides aat Layer 7, the Application Layer. Layers 3–6 are not used.<ref>instrumentationtools ''https://instrumentationtools.com/hart-communication-tutorial-part-3/'' </ref> When sent over [[current loop|4–20&nbsp;mA]] it uses a [[Bell 202 modem|Bell 202]] for layer 1. But it is often converted to RS485 or RS232.

According to Emerson,<ref>Emerson ''https://web.archive.org/web/20181107104043/https://www.automation.com/automation-news/industry/emerson-proves-advancements-in-eddl-electronic-device-description-language-technology'', rev. 2005-04-14</ref> due to the huge installation base of 4–20 mA systems throughout the world, the HART Protocol is one of the most popular industrial protocols today. HART protocol has made a good transition protocol for users who wished to use the legacy 4–20 mA signals, but wanted to implement a "smart" protocol.

==OSI layer==

{| class="wikitable" style="margin: 1em auto 1em auto;"

|+ OSI model

|-

! colspan="4" |

! Wired FSK/PSK & RS485

! Wireless 2.4GHz

|-

! colspan="3" | Layer

! [[Protocol data unit]] (PDU)

! colspan="2" | HART

|-

! rowspan="4" | Host<br />layers

| style="background:#d8ec9b;" | 7

| style="background:#d8ec9b;" | [[Application layer|Application]]

| style="background:#d8ec9c;" rowspan="3" | [[Data (computing)|Data]]

| style="background:#d8ec9c;" colspan="2" | Command-oriented. Data types and application procedures.

|-

| style="background:#d8ec9b;" | 6

| style="background:#d8ec9b;" | [[Presentation layer|Presentation]]

| style="background:#d8ec9b;" colspan="2"|

|-

| style="background:#d8ec9b;" | 5

| style="background:#d8ec9b;" | [[Session layer|Session]]

| style="background:#d8ec9b;" colspan="2"|

|-

| style="background:#e7ed9c;" | 4

| style="background:#e7ed9c;" | [[Transport layer|Transport]]

| style="background:#e7ed9c;" | [[Packet segmentation|Segment]], [[datagram]]

| style="background:#e7ed9c;" colspan="2"| Auto-segmented transfer of large data sets, negotiated segment sizes

|-

! rowspan="3" | Media<br />layers

| style="background:#eddc9c;" | 3

| style="background:#eddc9c;" | [[Network layer|Network]]

| style="background:#eddc9c;" | [[Network packet|Packet]]

| style="background:#eddc9c;" |

| style="background:#eddc9c;" | Wireless [[Mesh_networking|mesh network]], power-optimized

|-

| style="background:#e9c189;" | 2

| style="background:#e9c189;" | [[Data link layer|Data link]]

| style="background:#e9c189;" | [[Frame (networking)|Frame]]

| style="background:#e9c189;" | A [[Binary operation|binary]], [[byte]]-oriented, token passing, master/slave

| style="background:#e9c189;" | Wireless, time synced, [[Time-division_multiple_access|TDMA]], [[Automatic repeat request|ARQ]]

|-

| style="background:#e9988a;" | 1

| style="background:#e9988a;" | [[Physical layer|Physical]]

| style="background:#e9988a;" | [[Bit]], [[Symbol rate#Symbols|symbol]]

| style="background:#e9988a;" | Analog and digital signaling, normally 4-20mA or RS485 copper wiring.

| style="background:#e9988a;" | 2.4GHz wireless, 802.15.4-based radios, 10[[dBm]] Tx power

|}

==History==

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| Address size

|colspan="2"| Number of Expansion bytes

|colspan="2"| PhysialPhysical layer type

|colspan="3"| Frame type

|}

;bit 7, if high use Unique (5 byte) address, else use PolingPolling (1 Byte) addresses.

;bit 6 and 5, Number of Expansion bytes: normally it set if Expansion field is used, normally 0.

;bit 4 and 3, PhysialPhysical layer type: 0=Asynchronous, <br> 1=Synchronous

;bit 2, 1 and 0, Frame type: 1=BACK Burst Acknowledge send by Burst-mode Device<br> 2=STX Master to Field Devices.<br> 6=Slave Acknowledge to STX frame.

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==External links==

* [http://www.FieldCommGroup.org/ FieldComm Group]

* [http://hartprotocollite.codeplex.com/ .NET Open Source project] {{Webarchive|url=https://web.archive.org/web/20171223221824/http://hartprotocollite.codeplex.com/ |date=2017-12-23 }}

{{List of automation protocols}}