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{{Short description|Communications protocol}}
{{Infobox fieldbus protocol
| Name              = Profibus
| image             = PROFIBUS rgb 2010.png
| image_size        = 121px
| Type_of_Network   = Device bus, [[industrial process control]]
| Physical_Media    = [[Twisted pair]], fiber
| Network_Topology  = Bus
| Device_Addressing = [[DIP switch]] or hardware/software
| Governing_Body    = PROFIBUS&PROFINET International (PI)
| URL               = {{URL|https://www.profibus.com/}}
}}
[[File:0x-pb-stecker-verschieden.jpg|thumb|Profibus electrical connector]]

'''Profibus''' (usually styled as ''PROFIBUS'', as a [[portmanteau]] for <u>Pro</u>cess <u>Fi</u>eld <u>Bus</u>) is a standard for [[fieldbus]] communication in [[automation]] technology and was first promoted in 1989 by [[BMBF]] (German department of education and research) and then used by [[Siemens]].<ref name="weigmann" /> It should not be confused with the [[Profinet]] standard for [[Industrial Ethernet]]. Profibus is openly published as type 3 of IEC 61158/61784-1.<ref name="iec61784-1" />

== Origin ==
The history of PROFIBUS goes back to a publicly promoted plan from Marco Todaro for an association which started in Germany in 1986 and for which 18 companies and institutes devised a master project plan called "[[fieldbus]]".<ref name=book /> The goal was to implement and spread the use of a [[bit-serial]] field bus based on the basic requirements of the field device interfaces. For this purpose, member companies agreed to support a common technical concept for production (i.e. discrete or factory [[automation]]) and [[process automation]]. First, the complex communication protocol Profibus FMS (Field bus Message Specification), which was tailored for demanding communication tasks, was specified. Subsequently, in 1993, the specification for the simpler and thus considerably faster protocol PROFIBUS DP (Decentralised Peripherals) was completed. Profibus FMS is used for (non-deterministic) communication of data between Profibus Masters. Profibus DP is a protocol made for (deterministic) communication between Profibus masters and their remote I/O slaves.<ref name=PI4332 /><ref name=xiu3 />

There are two variations of PROFIBUS in use today; the most commonly used PROFIBUS DP, and the lesser used, application specific, PROFIBUS PA:
* '''PROFIBUS DP''' (Decentralised Peripherals)<ref name=mitchell /> is used to operate sensors and actuators via a centralised controller in production (factory) automation applications. The many standard diagnostic options, in particular, are focused on here.<ref name=PI8012 />
* '''PROFIBUS PA''' (Process Automation) <ref name=powel /> is used to monitor measuring equipment via a process control system in process automation applications. This variant is designed for use in explosion/hazardous areas ([[Electrical Equipment in Hazardous Areas#Zones (vapours & gases)|Ex-zone]] 0 and 1). The Physical Layer (i.e. the cable) conforms to IEC 61158-2,<ref name=iec61158-2/> which allows power to be delivered over the bus to field instruments, while limiting current flows so that explosive conditions are not created, even if a malfunction occurs. The number of devices attached to a PA segment is limited by this feature. PA has a data transmission rate of 31.25&nbsp;kbit/s. However, PA uses the same protocol as DP, and can be linked to a DP network using a coupler device. The much faster DP acts as a backbone network for transmitting process signals to the controller. This means that DP and PA can work tightly together, especially in hybrid applications where process and factory automation networks operate side by side.

In excess of 30 million PROFIBUS nodes were installed by the end of 2009. 5 million of these are in the process industries.<ref name=book />

== Technology ==
{| border="0" cellspacing="3" style="margin:1em auto"
|+ '''PROFIBUS Protocol ([[OSI reference model]])'''
! colspan="2" | OSI-Layer
! colspan="3" align="center" | PROFIBUS
|-----
| align="center" bgcolor="#ffff99" | 7
| align="center" bgcolor="#ffff99" | Application
| align="center" bgcolor="#ffcc99" | DPV0
| align="center" bgcolor="#ffcc99" | DPV1
| align="center" bgcolor="#ffcc99" | DPV2
| rowspan="7" align="center" bgcolor="#cccccc" | Management
|-----
| align="center" bgcolor="#ffff99" | 6
| align="center" bgcolor="#ffff99" | Presentation
| colspan="3" rowspan="4" align="center" bgcolor="#dddddd" | --
|-----
| align="center" bgcolor="#ffff99" | 5
| align="center" bgcolor="#ffff99" | Session
|-----
| align="center" bgcolor="#ffff99" | 4
| align="center" bgcolor="#ffff99" | Transport
|-----
| align="center" bgcolor="#ffff99" | 3
| align="center" bgcolor="#ffff99" | Network
|-----
| align="center" bgcolor="#ffff99" | 2
| align="center" bgcolor="#ffff99" | Data Link
| colspan="3" align="center" bgcolor="#ffcc99" | FDL
|-----
| align="center" bgcolor="#ffff99" | 1
| align="center" bgcolor="#ffff99" | Physical
| align="center" bgcolor="#ffcc99" | [[EIA-485]]
| align="center" bgcolor="#ffcc99" | Optical
| align="center" bgcolor="#ffcc99" | MBP<!--It means Manchester Bus Powered.-->
|}

=== Application layer (OSI-Layer 7) ===
To use these functions, various service levels<ref name=iec61158-5-3/> of the DP protocol<ref name=iec61158-6-3/> were defined:<ref name=PI4072/><ref name=xiu4 />
* DP-V0 for cyclic exchange of data and diagnosis
* DP-V1 for acyclic data exchange and alarm handling<ref name=xiu2 />
* DP-V2 for [[isochronous]] mode and data exchange broadcast ([[master/slave (technology)|slave]]-to-slave communication)

=== Data link layer (OSI-Layer 2) ===
The data link layer '''FDL''' (Field bus Data Link) services<ref name=iec61158-3-3/>and protocols<ref name=iec61158-4-3/> work with a hybrid access method that combines [[token passing]] with a master/slave method. In a PROFIBUS DP network, the controllers or process control systems are the masters and the sensors and actuators are the slaves.<ref name=PI4072/><ref name=felser />

Each byte has even parity and is transferred asynchronously with a start and stop bit.
There may not be a pause between a stop bit and the following start bit when the bytes of a telegram are transmitted. The master signals the start of a new telegram with a SYN pause of at least 33 bits (logical "1" = bus idle).

Various telegram types are used. They can be differentiated by their start [[delimiter]] (SD):

==== No data ====
SD1 = 0x10
{| border="1"
|bgcolor="#ffff99"|SD1
|bgcolor="#ffcc99"|DA
|bgcolor="#ffcc99"|SA
|bgcolor="#77ffff"|FC
|bgcolor="#ff7777"|FCS
|bgcolor="#ffff99"|ED
|}

==== Variable length data ====
SD2 = 0x68
{| border="1"
|bgcolor="#ffff99"|SD2||LE||LEr||bgcolor="#ffff99" |SD2
|bgcolor="#ffcc99"|DA
|bgcolor="#ffcc99"|SA
|bgcolor="#77ffff"|FC
|bgcolor="#99ff99"|DSAP
|bgcolor="#99ff99"|SSAP
||PDU
|bgcolor="#ff7777"|FCS
|bgcolor="#ffff99"|ED
|}

==== Fixed length data ====
SD3 = 0xA2
{| border="1"
|bgcolor="#ffff99"|SD3
|bgcolor="#ffcc99"|DA
|bgcolor="#ffcc99"|SA
|bgcolor="#77ffff"|FC
||PDU
|bgcolor="#ff7777"|FCS
|bgcolor="#ffff99"|ED
|}

==== Token ====
SD4 = 0xDC
{| border="1"
|bgcolor="#ffff99"|SD4
|bgcolor="#ffcc99"|DA
|bgcolor="#ffcc99"|SA
|}

==== Fields ====
{| class="wikitable" border="1"
| '''SD'''
| Start Delimiter
|-
| '''LE'''
| Length of protocol data unit, (incl. DA, SA, FC, DSAP, SSAP)
|-
| '''LEr'''
| Repetition of length of protocol data unit, (Hamming distance = 4)
|-
| '''FC'''
| Function Code
|-
| '''DA'''
| Destination Address
|-
| '''SA'''
| Source Address
|-
| '''DSAP'''
| Destination [[Service Access Point]]
|-
| '''SSAP'''
| Source [[Service Access Point]]
|-
| '''PDU'''
| Protocol Data Unit (protocol data)
|-
| '''FCS'''
| [[Frame check sequence|Frame Checking Sequence]], calculated by simply adding up the bytes within the specified length. An overflow is ignored here.
|-
| '''ED'''
| End Delimiter (= 0x16)
|}

==== Service Access Points ====
{| class="wikitable" border="1"
! SAP (Decimal)
! SERVICE
|-
| Default 0
| Cyclical Data Exchange (Write_Read_Data)
|-
| 54
| Master-to-Master SAP (M-M Communication)
|-
| 55
| Change Station Address (Set_Slave_Add) – SAP55 is optional and may be disabled if the slave doesn't provide non-volatile storage memory for the station address.
|-
| 56
| Read Inputs (Rd_Inp)
|-
| 57
| Read Outputs (Rd_Outp)
|-
| 58
| Control Commands to a DP Slave (Global_Control)
|-
| 59
| Read Configuration Data (Get_Cfg)
|-
| 60
| Read Diagnostic Data (Slave_Diagnosis)
|-
| 61
| Send Parameterization Data (Set_Prm)
|-
| 62
| Check Configuration Data (Chk_Cfg)
|}

=== Bit-transmission layer (OSI-Layer 1) ===
Three different methods are specified for the bit-transmission layer:<ref name=iec61158-2/>
* With electrical transmission<ref name=PI8032/><ref name=xiu1 /> pursuant to [[EIA-485]], [[twisted pair]] cables with [[characteristic impedance|impedances]] of 150 [[ohm]]s are used in a [[bus topology]].<ref name=PI8022/> [[Bit rate]]s from 9.6 kbit/s to 12 Mbit/s can be used. The cable length between two [[repeater]]s is limited from 100 to 1200&nbsp;m, depending on the bit rate used. This transmission method is primarily used with PROFIBUS DP.
* With optical transmission via [[fiber optics]], [[star topology|star-]], [[bus topology|bus-]] and [[ring topology|ring-topologies]] are used. The distance between the repeaters can be up to 15&nbsp;km. The ring topology can also be executed redundantly.<ref name=felser />
* With MBP (Manchester Bus Powered) <ref name=xiu1 /> transmission technology, data and field bus power are fed through the same cable. The power can be reduced in such a way that use in explosion-hazardous environments is possible. The bus topology can be up to 1900&nbsp;m long and permits branching to field devices (max. 60&nbsp;m branches). The bit rate here is a fixed 31.25&nbsp;kbit/s. This technology was specially established for use in process automation for PROFIBUS PA.<ref name=felser />

For data transfer via sliding contacts for mobile devices or optical or radio data transmission in open spaces, products from various manufacturers can be obtained, however they do not conform to any standard.

'''PROFIBUS DP'''<ref name=mitchell /> uses two core screened cable with a violet sheath,<ref name=PI8032/> and runs at speeds between 9.6&nbsp;kbit/s and 12&nbsp;Mbit/s.<ref name=PI8022/> A particular speed can be chosen for a network to give enough time for communication with all the devices present in the network. If systems change slowly then lower communication speed is suitable, and if the systems change quickly then effective communication will happen through faster speed. The RS485 balanced transmission used in PROFIBUS DP only allows 31 devices to be connected at once; however, more devices (up to 126) can be connected or the network expanded with the use of hubs or repeaters (4 hubs or repeaters to reach 126).<ref name=PI8012/> A Hub or a Repeater is also counted as a device.<ref name=iec61784-5-3/>

'''PROFIBUS PA'''<ref name=powel /> runs at fixed speed of 31.25&nbsp;kbit/s via blue sheathed two core screened cable. The communication may be initiated to minimise the risk of explosion or for the systems that intrinsically need safe equipment. The message formats in PROFIBUS PA are identical to PROFIBUS DP.

Note: PROFIBUS DP and PROFIBUS PA should not be confused with [[PROFINET]].

== Profiles ==
Profiles are pre-defined configurations of the functions and features available from PROFIBUS for use in specific devices or applications. They are specified by PI working groups and published by PI. Profiles are important for openness, interoperability and interchangeability, so that the end user can be sure that similar equipments from different vendors perform in a standardised way. User choice also encourages competition that drives vendors towards enhanced performance and lower costs.

There are PROFIBUS profiles for Encoders, Laboratory instruments, [[Intelligent pump]]s, Robots and Numerically Controlled machines, for example. Profiles also exist for applications such as using HART and wireless with PROFIBUS, and process automation devices via PROFIBUS PA. Other profiles have been specified for Motion Control (PROFIdrive) and Functional Safety ([[PROFIsafe]]).

== Organization ==
The ''PROFIBUS Nutzerorganisation e.V.'' (PROFIBUS User Organisation, or PNO) was created in 1989.<ref name=book /> This group was composed mainly of manufacturers and users from Europe. In 1992, the first regional PROFIBUS organisation was founded (PROFIBUS Schweiz in Switzerland). In the following years, additional Regional PROFIBUS & PROFINET Associations (RPAs) were added.

In 1995, all the RPAs joined together under the international umbrella association Profibus and Profinet International (PI). Today, PROFIBUS is represented by 25 RPAs around the world (including PNO) with over 1400 members, including most if not all major automation vendors and service suppliers, along with many end users.

== See also ==
* [[Fieldbus]]
* [[List of automation protocols]]

== References ==
<References>
<!--- IEC standards --->
<ref name=iec61784-1> {{cite web |url=https://webstore.iec.ch/en/iec-search/result?q=61784-1 |title=Industrial communication networks - Profiles Part 1: Fieldbus profiles |date=2019 |id=IEC 61784-1 |publisher=International Electrotechnical Commission (IEC) |access-date=2020-04-28 }}</ref>
<ref name=iec61158-2> {{cite web |url=https://webstore.iec.ch/en/iec-search/result?q=61158-2 |title=Industrial communication networks - Fieldbus specifications - Part 2: Physical layer specification and service definition |date=2022 |id=IEC 61158-2 |publisher=International Electrotechnical Commission (IEC) |access-date=2023-02-09 }}</ref>
<ref name=iec61158-3-3> {{cite web |url=https://webstore.iec.ch/en/iec-search/result?q=61158-3-3 |title=Industrial communication networks - Fieldbus specifications - Part 3-3: Data-link layer service definition - Type 3 elements |date=2014 |id=IEC 61158-3-3 |publisher=International Electrotechnical Commission (IEC) |access-date=2023-02-09 }}</ref>
<ref name=iec61158-4-3> {{cite web |url=https://webstore.iec.ch/en/iec-search/result?q=61158-4-3 |title=Industrial communication networks - Fieldbus specifications - Part 4-3: Data-link layer protocol specification - Type 3 elements |date=2019 |id=IEC 61158-4-3 |publisher=International Electrotechnical Commission (IEC) |access-date=2023-02-09 }}</ref>
<ref name=iec61158-5-3> {{cite web |url=https://webstore.iec.ch/en/iec-search/result?q=61158-5-3 |title=Industrial communication networks - Fieldbus specifications - Part 5-3: Application layer service definition - Type 3 elements |date=2014 |id=IEC 61158-5-3 |publisher=International Electrotechnical Commission (IEC) |access-date=2023-02-09 }}</ref>
<ref name=iec61158-6-3> {{cite web |url=https://webstore.iec.ch/en/iec-search/result?q=61158-6-3 |title=Industrial communication networks - Fieldbus specifications - Part 6-3: Application layer protocol specification - Type 3 elements |date=2019 |id=IEC 61158-6-3 |publisher=International Electrotechnical Commission (IEC) |access-date=2023-02-09 }}</ref>
<ref name=iec61784-5-3> {{cite web |url=https://webstore.iec.ch/en/iec-search/result?q=61784-5-3 |title=Industrial communication networks - Profiles - Part 5-3: Installation of fieldbuses - Installation profiles for CPF 3 |date=2018 |id=IEC 61784-5-3 |publisher=International Electrotechnical Commission (IEC) |access-date=2023-02-09 }}</ref>

<!--- PI documents --->
<ref name=book >{{cite book |last1=Bender |first1=Klaus |last2=Freitag |first2=Jörg |last3=Lindner |first3=Klaus-Peter |date=2009
 |title=Milestones: PROFIBUS - 20 years of standards for industrial communication |url=https://drive.google.com/file/d/1ag2aZhKQADhMJwgh79o9oBX37X7mptIE/view?usp=sharing |location=Karlsruhe |publisher=PROFIBUS Nutzerorganisation e.V. }}</ref>
<ref name=PI4332> {{cite web |url=https://www.profibus.com/download/profibus-technology-and-application-system-description/ |title=PROFIBUS Technology and Application – System Description |date=2016 |id=Order no. 4.332 |publisher=Profibus and Profinet International (PI) |access-date=2023-02-09 }}</ref>
<ref name=PI4072> {{cite web |last=Popp |first=Manfred |url=https://www.profibus.com/download/book-the-new-rapid-way-to-profibus-dp |title=The New Rapid Way to PROFIBUS DP - From DP-V0 to DP-V2 |date=2003 |id=Order no. 4.072 |publisher=Profibus and Profinet International (PI) |access-date=2023-02-09 }}</ref>
<ref name=PI8012> {{cite web |url=https://www.profibus.com/download/profibus-installation-guidelines |title=PROFIBUS Design |date=2020 |id=Order no. 8.012 |publisher=Profibus and Profinet International (PI) |access-date=2023-02-09 }}</ref> 
<ref name=PI8022> {{cite web |url=https://www.profibus.com/download/profibus-installation-guidelines |title=PROFIBUS Cabling and Assembly |date=2020 |id=Order no. 8.022 |publisher=Profibus and Profinet International (PI) |access-date=2023-02-09 }}</ref> 
<ref name=PI8032> {{cite web |url=https://www.profibus.com/download/profibus-installation-guidelines |title=PROFIBUS Commissioning |date=2022 |id=Order no. 8.032 |publisher=Profibus and Profinet International (PI) |access-date=2023-02-09 }}</ref>

<!--- Books --->
<ref name=weigmann >{{cite book |last1=Weigmann |first1=Josef |last2=Kilian |first2=Gerhard |date=2003 |title=Decentralization with PROFIBUS DP/DPV1: Architecture and Fundamentals, Configuration and Use with SIMATIC S7 |publisher=Siemens |isbn=978-3-89578-218-3 }}</ref>
<ref name=powel >{{cite book |last1=Powel |first1=James |last2=Vandeline |first2=Henry |date=2012 |title=Catching the Process Fieldbus: An Introduction to Profibus for Process Automation |publisher=Momentum Press |isbn=978-1606503966 }}</ref>
<ref name=mitchell >{{cite book |last=Mitchell |first=Ronald |date=2003 |title=PROFIBUS: A Pocket Guide |publisher=ISA |isbn=978-1556178627 }}</ref>
<ref name=felser >{{cite book |last=Felser |first=Max |date=2017 |title=PROFIBUS Manual |publisher=epubli GmbH |url=https://felser.ch/profibus-manual |isbn=978-3-8442-1435-2 }}</ref>
<ref name=xiu1 >{{cite book |last=Xiu |first=Ji |date=2013 |title=PROFIBUS in Practice: Installing PROFIBUS devices and cables |publisher=CreateSpace Independent Publishing Platform |isbn=978-1481245210 }}</ref>
<ref name=xiu2 >{{cite book |last=Xiu |first=Ji |date=2013 |title=PROFIBUS in Practice: System Engineering, Trouble-shooting and Maintenance  |publisher=CreateSpace Independent Publishing Platform |isbn=978-1493614684 }}</ref>
<ref name=xiu3 >{{cite book |last=Xiu |first=Ji |date=2015 |title=PROFIBUS in Practice: System Architecture and Design  |publisher=CreateSpace Independent Publishing Platform |isbn=978-1507633045 }}</ref>
<ref name=xiu4 >{{cite book |last=Xiu |first=Ji |date=2019 |title=PROFIBUS in Practice: Standard and Operation |publisher=Independently Published |isbn=978-1793076830 }}</ref>

</references>

== External links ==
* [https://www.profibus.com/ PROFIBUS & PROFINET International]

{{Automation protocols}}
{{Computer-bus}}
{{Authority control}}

[[Category:Industrial computing]]
[[Category:Serial buses]]
[[Category:Industrial automation]]
[[Category:Computer-related introductions in 1989]]