Digital Transformation Group
Operational Technology
Design Standard DS 43-04
Profinet and Profibus Network Design and Installation
VERSION 2
REVISION 0
NOVEMBER 2018
Design Standard No. DS 43-04
Profinet and Profibus Network Design and Installation
FOREWORD
SCADA Design Standards are prepared to ensure that the Water Corporation’s staff, consultants and
contractors are informed as to the Water Corporation’s design standards and recommended practices. Design
standards are intended to promote uniformity so as to simplify design and drafting practice and have as their
ultimate objective the provision of safe and functional plant at minimum whole of life cost.
The Water Corporation design standards and recommended practices described in this design standard have
evolved over a number of years as a result of design and field experience and these have been investigated
and documented.
Deviation, on a particular project, from the design standards and recommended practices may be permitted in
special circumstances but only after consultation with and endorsement by the Principal Engineer, SCADA
in the Water Corporation’s Operational Technology.
Users are invited to forward submissions for continuous improvement to the Principal SCADA Engineer
who will consider these for incorporation into future revisions.
Head of Operational Technology
This document is prepared without the assumption of a duty of care by the Water Corporation. The document is not
intended to be nor should it be relied on as a substitute for professional engineering design expertise or any other
professional advice.
It is the responsibility of the user to ensure they are using the current version of this document.
© Copyright – Water Corporation: This standard and software is copyright. With the exception of use permitted by the
Copyright Act 1968, no part may be reproduced without the written permission of the Water Corporation.
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Profinet and Profibus Network Design and Installation
REVISION STATUS
The revision status of this standard is shown section by section below:
REVISION STATUS
VER/ DATE
PAGES
REV
REVISED
0/0
08.08.07
All
REVISION DESCRIPTION
RVWD. APRV.
(Section, Clause, Sub-Clause)
New Edition, draft release for
commenting of chapter 1 – 3.
Added Chapter 4, minor
changes to remainder
General Revision after initial
LR
SE
review
1.3: Added DS 80 reference
FW
JGB
1.4: Added more definitions
1.9: New section
1.10: New section
2.5: Revised DP cycle time
formula
2.6: Reduced max permissible
cable length for lower baud
rates to 1000m.
Amended 500 Kbit/s allowance
statement.
2.8: Reworded and amended last
paragraph to remove ambiguity
regarding termination
requirements with repeaters.
Amended figure 11
2.9: Reworded section to remove
ambiguity.
5.3: New section
6.5: New section
6.6: New section
6.7: New section
0/1
30.08.07
Chapter 4
1/0
14.03.08
All
1/1
22.09.08
Various
2/0
22.03.18
Revised
Draft release of Profinet
FW
Chapters: 1.2 addition as discussion paper for
review meeting
1.4
1.6
1.7
1.10
4.2 (old 3.2)
5 and all its
subchapters
(old chapter 4)
6 and all its
subchapters
(old chapter 5)
JGB
New Chapters:
2
7.8
7.9
2/0
12/11/18
Final release of Profinet
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JGB
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Profinet and Profibus Network Design and Installation
REVISION STATUS
VER/ DATE
PAGES
REV
REVISED
REVISION DESCRIPTION
(Section, Clause, Sub-Clause)
additions
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Design Standard No. DS 43-04
Profinet and Profibus Network Design and Installation
Design Standard DS 43-04
Profinet and Profibus
CONTENTS
Section
Page
1
Introduction ...................................................................................................................................8
1.1
Purpose..........................................................................................................................................8
1.2
Scope..............................................................................................................................................8
1.3
References .....................................................................................................................................8
1.4
Definitions .....................................................................................................................................9
1.5
Standards ....................................................................................................................................13
1.6
Guidelines ...................................................................................................................................13
1.7
Further reference documents ....................................................................................................13
1.8
Mandatory Requirements .........................................................................................................13
1.9
Mandatory Documentation Deliverables .................................................................................13
1.10
Mandatory Design and Installation Certification ...................................................................14
2
Profinet Design ............................................................................................................................15
2.1
2.1.1
2.1.2
2.1.3
2.1.4
Topology......................................................................................................................................15
Line Topology (NOT to be used) .................................................................................................15
Star Topology ...............................................................................................................................16
Tree Topology (NOT to be used) .................................................................................................16
Media Redundancy Protocol (MRP) Ring Topology (to be used) ...............................................17
2.2
I/O Devices requirements ..........................................................................................................18
2.3
Ethernet switches requirements................................................................................................18
2.4
Number of I/O Devices per Network ........................................................................................19
2.5
Device Names ..............................................................................................................................20
2.6
IP addresses ................................................................................................................................20
2.7
Update Times ..............................................................................................................................21
2.8
Network load ..............................................................................................................................21
2.9
SCADA and OIP connections ...................................................................................................24
2.10
Number of I/O Controllers per Profinet Network ..................................................................24
2.11
Inter PLC communication.........................................................................................................26
2.12
Siemens S7 H-Systems ...............................................................................................................26
2.13
Device Certification....................................................................................................................28
2.14
Cable and Connector Specification ..........................................................................................28
2.15
Cable length ................................................................................................................................28
2.16
Integration of Profibus PA devices ...........................................................................................28
2.17
Integration of Profibus DP Slave devices .................................................................................29
2.18
Designer Checklist......................................................................................................................31
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3
Profibus DP Design .....................................................................................................................32
3.1
3.1.1
Topology......................................................................................................................................32
Fibre optic ....................................................................................................................................32
3.1.1.1 Fibre Optic Linear bus (Line) Topology ......................................................................33
3.1.1.2 Fibre Optic (redundant) Ring Topology .......................................................................33
3.1.1.3 Fibre Optic Star Topology ............................................................................................34
RS 485 (copper) ...........................................................................................................................34
3.1.2.1 RS 485 Linear bus (Line) Topology .............................................................................35
3.1.2.2 RS 485 Tree Topology .................................................................................................35
3.1.2
3.2
Number of Devices per RS 485 Segment ..................................................................................35
3.3
Node Addresses ..........................................................................................................................36
3.4
Number of Nodes on a Profibus network .................................................................................37
3.5
Bus cycle time .............................................................................................................................37
3.6
Bus speed & Segment Cable Length.........................................................................................38
3.7
Spurlines .....................................................................................................................................39
3.8
Termination ................................................................................................................................40
3.9
Certification ................................................................................................................................42
3.10
Cable specification .....................................................................................................................42
4
Profibus PA Design .....................................................................................................................44
4.1
Topology......................................................................................................................................44
4.2
DP/PA Link and Coupler selection...........................................................................................44
4.3
Number of PA Devices per Segment/Coupler..........................................................................48
4.4
Spurlines, Splices and Cable length..........................................................................................48
4.5
Segment Current consumption and Voltage Drop calculations.............................................49
4.6
Bus cycle time .............................................................................................................................50
4.7
Termination ................................................................................................................................51
4.8
Device Manager PC ...................................................................................................................51
4.9
Certification ................................................................................................................................52
4.10
Cable specification .....................................................................................................................52
4.11
Explosion Safety .........................................................................................................................52
5
Installation ...................................................................................................................................54
5.1
Shield connection........................................................................................................................54
5.2
Cable handling and protection..................................................................................................54
5.3
Cable spacing ..............................................................................................................................55
5.4
Fast connect system ....................................................................................................................56
5.5
Minimum Profibus DP cable length between devices .............................................................56
5.6
DB9 Connectors and Profibus installation cable path ............................................................56
6
PLC and SCADA configuration ................................................................................................58
6.1
6.1.1
PLC configuration......................................................................................................................58
GSD files ......................................................................................................................................58
6.1.1.1 Profibus.........................................................................................................................58
6.1.1.2 Profinet .........................................................................................................................58
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6.1.2
6.1.3
Device Watchdog time (Response monitoring) ...........................................................................58
DP Master or I/O Controller bus monitoring ...............................................................................58
6.2
6.2.1
6.2.2
Diagnostics ..................................................................................................................................59
Profibus Diagnostics ....................................................................................................................59
Profinet Diagnostics .....................................................................................................................60
6.3
Profibus DP Bus parameters .....................................................................................................61
7
Appendix ......................................................................................................................................62
7.1
List of figures ..............................................................................................................................62
7.2
List of Tables ..............................................................................................................................62
7.3
List of Equations ........................................................................................................................63
7.4
7.4.1
7.4.2
7.4.3
7.4.4
Explanatory notes for Topology drawing 1 (Profibus with Siemens PA Link/Coupler) .....64
Estimated DP cycle time: .............................................................................................................65
Estimated PA cycle time: .............................................................................................................65
PA current consumption: .............................................................................................................65
PA Voltage drop calculation: .......................................................................................................66
7.5
7.5.1
7.5.2
7.5.3
7.5.4
Explanatory notes for Topology drawing 2 (Profibus with P&F PA Link/Coupler) ...........66
Estimated DP cycle time: .............................................................................................................67
Estimated PA cycle time: .............................................................................................................68
PA current consumption: .............................................................................................................68
PA Voltage drop calculation: .......................................................................................................68
7.6
7.6.1
Explanatory notes for Topology drawing 3 (Profibus with pure DP network, no PA)........69
Estimated DP cycle time: .............................................................................................................69
7.7
7.7.1
Explanatory notes for Topology drawing 4 (pure Profinet) ...................................................69
Estimated Network load: ..............................................................................................................71
7.8
7.8.1
Explanatory notes for Topology drawing 5 (Profinet with GSDML file based PA proxy) .72
Estimated Network load: ..............................................................................................................73
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1
Introduction
1.1
Purpose
The Water Corporation has adopted a policy of outsourcing most of the electrical engineering and
electrical detail design associated with the procurement of its assets. The resulting assets need to be in
accordance with the Corporation’s operational needs and standard practices.
This document sets out design standards and engineering practices which shall be followed in respect
to the design and specification of electrical works being acquired by the Corporation.
While this design standard aims to be comprehensive, the Designer shall not assume that it covers all
requirements for a particular application.
It is the Water Corporation’s objective that its assets will be designed so that these are fit for purpose,
have a minimum long term cost and are safe to operate and maintain. In respect to matters not covered
specifically in this standard, the Designer shall aim their designs and specifications at achieving this
objective.
1.2
Scope
The scope of this standard covers in detail aspects of Profibus and Profinet design, configuration and
installation which are particular to the Water Corporation’s requirements for water and wastewater
assets.
1.3
References
References should be made also to the following associated design standards:
DS 24
Electrical Drafting
DS 40-02
Naming Convention
DS 40-09
Electronic Instrumentation
DS 80
WCX CAD Standard
Approved Equipment List
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1.4
Definitions
ARP
Address Resolution Protocol, a vendor-neutral protocol to map a Network address (
e.g. IPV4 address) to a physical address (e.g. MAC address)
Conformance Classes
Three types of Conformance Classes (CC) exist in Profinet
CC-A: Provides basic Profinet functionality such as
• Cyclic I/O
• Acyclic Parameter data
• Device Diagnostics (Alarms)
• Device identification via I&M (Information and Maintenance data)
• Topology (Neighbourhood detection via LLDP)
CC-B: Extends CC-A by adding:
• Network diagnostics via SNMP
• Topology information via MIBS to enable SNMP readout
• Integration of Switches as IO-Devices to enable network diagnostics
from the I/O Controller via Profinet
• System redundancy (CC-B PA)
CC-B features make it the preferred Conformance Class for Process Automation
CC-C: Extends CC-B by adding hardware based Isochronous Real time mode to it as
required for example by Motion control applications. CC-C has no relevance for the
Process Control Industry
Designer
The person or company engaged by Water Corporation to design the part of the
asset relevant to this standard
Diagnostic Repeater
Regenerates the Profibus-DP RS485 signal in the same manner as the
standard Repeater. Additional functionality allows the monitoring of the
copper cable up to 100m from the repeater on legs 2 and 3. Leg 1 in intended
to be connected closely to the Master PLC.
Allows monitoring of Profibus-DP copper networks from the HMI.
DP/DP coupler
Used to link two separate Profibus-DP networks together to allow data exchange
between two Masters (Siemens terminology).
DP Master
A DP Master is responsible for handling the bus and is typically the PLC (GE
Fanuc, Modicon, Siemens etc.). There has to be at least one DP Master on a
Profibus but there may be more than one.
DP Master functionalities:
Class 1 DP master: This is the central component of PROFIBUS DP. A Class 1 DP
master exchanges information with the distributed stations in a defined, recurring
message cycle.
Class 2 DP master: Devices of this type are programming, configuration and/or
operator Panels/PC’s. A Class 2 DP master can for example read inputs & outputs,
request diagnostic information and may also facilitate DP Slave configuration.
DP Slave
A DP Slave “belongs” to a DP Master. DP Slaves can be remote I/O stations,
Control Valves, Flowmeters etc.
DP slave functionalities:
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DP-V0 (basic functionality): For configuration, parameterization, cyclic reading of
inputs, writing of outputs and reading of diagnosis data.
DP-V1: Acyclical services for the writing and reading of parameters and data
records (realised with low priority and parallel to the rapid cyclical user data
transfer). DP-V1 is an optional function extensions and compatible with the DPV0
basic functionality.
DP-V2: Support for Slave to Slave Internode communications and clocksynchronization (equidistant Profibus). DP-V2 is an optional function extensions
and compatible with the DPV0 and V1 functionality.
DP/PA Link
Used as a message buffer between PA couplers and the DP bus to allow operation
of the DP network at higher/PA bus independent speeds (Siemens terminology,
called “DP/PA Gateway” if P&F is used)
FISCO
Fieldbus Intrinsically Safe Concept.
Gap factor
Determines how many token cycles the master will do before doing a search for a
new master on the bus.
GSD File
German acronym for “Geräte Stammdaten Datei”, commonly referred to as
“Generic Station Description” file in English. A GSD file is nothing more than a
simple text file which contains a description of the functionality of a DP or PA
Slave in a standardised form. GSD files for DP or PA Slaves are required for the
configuration of the DP Master.
GSDML file
A GSD file written in XML (Extensible Markup Language) and used for Profinet
I/O Devices
HSA
Highest Station Address. The highest permissible Master address within a
Profibus-DP network. The default value of 126 shall be used.
I/O Controller
Comparable to a Class 1 DP Master in Profibus, the I/O Controller is typically the
PLC which is responsible for the I/O Devices configuration and provides them with
cyclic output data while receiving (consuming) input data from them.
I/O Device
Comparable to a DP Slave in Profibus, the I/O Device is a distributed field device
that belongs to a at least one I/O Controller. An I/O Device is the provider of input
data and the consumer of output data.
I/O Supervisor
Essentially identical to the role of a Class 2 Master in Profibus, I/O Supervisors
examples are Programming stations, HMIs and/or Diagnostic PCS. An I/O
Supervisor can for example read inputs & outputs, request diagnostic information
and may also facilitate I/O Device parameterisation (e.g. Device Name assignment,
IP address assignment)
kbit/s
Kilo bits per second, unit for Profibus transmission/bus speeds
Max. TSDR
Maximum Station Delay Responder Time (in tBits). The maximum time a Slave
could need before starting to send a response.
Min. TSDR
Minimum Station Delay Responder Time (in tBits). The minimum time a Slave
shall wait before starting to send a response. Recommend value is 22 irrespective
of bus speed which “calms” the bus without unduly increasing bus cycle time.
MBP
Manchester Bus Powered. Physical signal level layer (Layer 1) of Profibus-PA. It
uses synchronous Manchester coding on (typically) shielded twisted pair cable
which also carries the power for the instrument or device.
MRP
Media Redundancy Protocol in accordance with IEC 62439, a vendor-neutral
protocol to cater for copper or fibre optic based Ethernet OLM
Optical Link Module (Siemens terminology). Converts Profibus-DP from RS485
signal level to fibre optic and vice versa. Used to extend the physical Profibus
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network range and/or provide immunity against electrical interference or lightning
strikes.
PA Slave
A PA Slave “belongs” to a DP Master. PA Slaves are Analogue devices such as
Temperature, Pressure, Level, Flowmeters etc. PA Slaves can also receive their
power from the PA bus.
PA Coupler
Allows connection of a (Manchester Bus Powered) PA network to a (RS 485) DP
network. A PA coupler is responsible for the physical signal conversion between
the two networks and powering of the PA bus (Siemens terminology, called “PA
Segment Coupler” or “PA Power module” if P&F is used). PA couplers that are
directly connected to the DP bus require the DP network to run at low speeds
(45.45 or 93.75 Kbit/s).
PI
Profibus International. Profibus User Organisation responsible for governance of
Profibus.
Profibus
Process Field Bus. Industrial Fieldbus system in accordance with IEC 61158 Type
1 and 3 (encompasses Profibus-DP and PA).
Profibus-DP
Profibus for Decentralised Periphery. DP is synonym for cyclic high speed data
exchange between a Master (e.g. PLC) and a number of (distributed) Slaves (e.g.
I/O stations, instruments, devices) via RS485 or fibre optic based connections.
Profibus-PA
Profibus for Process Automation. PA is essentially a transparent extension of
Profibus-DP for the replacement of 4-20mA technology in the process industry. It
superimposes Profibus-DP on the MBP physical layer which uses only two wires
for instrument/device power supply and Profibus communication.
Retry limit
Maximum number of successive attempts that the Master “retries” to get a response
from a Slave before declaring the Slave as faulty. A value of 5 is recommended for
this to allow the bus to “ride though” short lived interference without causing
Slaves dropouts.
RS 485
Physical signal level layer (Layer 1) of Profibus-DP. It uses asynchronous NRZ
(non-return to zero) data coding over shielded twisted pair cable.
Repeater
Regenerates the Profibus DP RS485 Signal in amplitude and time. Used to extend
the overall physical network length or allow additional devices to be connected to
the bus. Certain Repeaters also provide electrical isolation between two Profibus
DP segments.
tBit
A tBit is the time it takes to transmit one bit and commonly used for bus timing
calculations. The value of a tBit is: 1/baud rate.
TSlot
Slot time. Maximum time (in tBits) the Master waits for the reception of the start of
a response message (the first 11 bit long octet of the response message shall be
received within this time which starts after the last 11 bit long octet of the request
message has been sent). A retry will be initiated if a response message start is not
received with this time.
TSet
Setup Time (in tBits). The setup time is an additional waiting time which is started
before a message is sent.
TQuiet
Quiet time (in tBits). The time a sender of a message waits before he switches from
send to receive. The default values are 0 to 9 (baud rate dependent), recommend
value is 9 irrespective of the baud rate (the earliest a message can be received is
after the expiry of Min. Tsdr. A “0” value may lead to “flooding’ of the receive
channel with parts of the reflected sent message).
Profinet
Process Field Network. Industrial Ethernet based Fieldbus system in accordance
with IEC 61158/61784.
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LLDP
Link Layer Discovery Protocol, a vendor-neutral protocol used by Ethernet devices
for advertising their identity, capabilities, and neighbours in local area network
rings
Cut-through
A method by which a switch does not buffer the message frame completely but
instead evaluates it as it arrives. As soon as the Destination address is read from the
arriving message frame the switch will start forwarding the message frame to the
specific port that can access the addressed Device.
The delay introduced by this method is ~7 microseconds and independent of the
message length.
DCP
Discovery and Configuration Protocol, part of the Profinet protocol suite and used
by the engineering tool and I/O Controller to discover devices, identify device
information and configure device settings such as device name and IP address on a
Profinet network
DHCP
Dynamic Host Configuration Protocol, a standardised protocol that caters for
automatic IP address assignment via a DHCP Server.
LAN
Local Area Network
VLAN
Virtual LAN
QoS
Quality of Service, Profinet RT uses QoS to allow prioritisation of Profinet I/O
data over other traffic. Profinet RT frames are tagged with a priority code of 6
(second highest) in the IEEE 802.1Q VLAN header that is part of the Profinet
Ethernet message.
SNMP
Simple Network Management Protocol, a de facto standard for collecting and
organising information about devices on an Ethernet Network
MIB
Management Information Base, a collection of definitions that define the properties
of an object (which is used by SNMP tools).
MRP
Media Redundancy Protocol. A data network protocol standardized by the
International Electrotechnical Commission as IEC 62439-2. It allows rings of
Ethernet switches to overcome any single failure.
Store and forward A method by which a switch stores the message frame completely and places them
in a queue. Switches that support QoS then priorities forwarding of the message
frame to the specific port that can access the addressed Device.
The delay introduced by this method varies depending on message length and
ranges from ~10 microseconds for a 64 Bytes long message frame and up to ~130
microseconds for a 1500 Byte long message frame.
MAC address
Media Access Control address, a physical address that is unique to every device,
generally assigned by the device manufacturer and coded into the Devices
hardware.
PN/DP Proxy
A device that allows integration of Profibus DP Slaves into a Profinet Network
PN/PA Proxy
A device that allows integration of Profibus PA Devices into a Profinet Network
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1.5
Standards
IEC 61158: Digital data communications for measurement and control - Fieldbus for use in industrial
control systems (Relevant parts: Type 1 and 3)
IEC 61784: Profile Set for Continuous and Discrete manufacturing relative to Fieldbus use in
industrial control systems (Relevant parts: Profile 3/1, 3/2 and 3/5-3)
IEC 1158-2:
Profibus PA physical Layer
IEC 61000: Installation and mitigation guidelines - Part 5-2 Earthing and cabling
IEC 60364: Electrical installations of buildings - Part 5-54: Selection and erection of electrical
equipment - Earthing arrangements, protective conductors and protective bonding
conductors.
IEC 60079 Electrical apparatus for explosive gas atmospheres
Part 11 – Intrinsic Safety “I”
Part 14 – Electrical installations in hazardous areas (other than mines)
Part 27 – Fieldbus Intrinsically Safe Concept (FISCO)
1.6
Guidelines
Profibus Assembling Guideline V1.14 (PI order number 8.022)
Profibus PA User and Installation Guideline V2.2 (PI order number: 2.092)
Profibus Interconnection Technology Guideline V1.4 (PI order number: 2.142)
Profibus Commissioning Guideline V1.09 (PI order number: 8.032)
Profibus Guidelines part 3, Diagnosis, Alarms and Time stamping (PI order number: 3.522)
Profinet Design Guideline V1.14 (PI order number 8.062)
Profinet Installation Guideline for Cabling and Assembly V1.0 (PI order number 8.072)
Profinet Cabling and Interconnection Technology V4.0 (PI order number 2.252)
Profinet Commissioning Guideline V1.36 (PI order number 8.082)
Profinet Security Guideline V2.0 (PI order number 7.002)
Profinet IO Conformance Classes V1.1 (PI order number 7.042)
1.7
Further reference documents
“Industrial Communication with PROFINET” by Manfred Popp (PI order number 4.182f)
“The New Rapid Way to PROFIBUS DP” by Manfred Popp
“Profibus PA – Instrumentation Technology for the Process Industry” by Ch. Diedrich and Th.
Bangermann.
1.8
Mandatory Requirements
In general the requirements of this standard are mandatory. No deviation from the requirements of
this standard shall be made without the written approval of the Principal SCADA Engineer. Any
request for deviation from the requirements of this standard put forward for approval shall still comply
with the Standards as listed in section 1.5 and Guidelines a listed in section 1.6.
1.9
Mandatory Documentation Deliverables
The Designer shall produce, sign off and submit the topology drawing(s) for each site to the Water
Corporation in accordance with requirements of Design Standard DS80 and shall also submit current
certificates as per section 3.9.
The topology drawing(s) for the particular project shall be based on the example topology drawings
JP05-72-01, 02, 03, 04 and 05 (refer also sections 7.5, 7.6, 7.7, 7.8 and 7.9).
The Designer shall ensure that the level of detail required by the Water Corporation as shown on the
example topology drawings is met.
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1.10
Mandatory Design and Installation Certification
The Designer shall be certified to perform Profinet and Profibus design by completing a Profinet and
Profibus training course offered by Profibus International or a course that has been approved by
Profibus International. The Design Engineer shall submit a copy of their current certification as proof.
Design engineers who are not certified but are involved in Profinet or Profibus design work shall be
closely supervised and their work shall be verified by a Profinet and Profibus certified design
engineer.
The Installer shall be certified to perform Profinet or Profibus installation by completing the relevant
training course offered by Profibus International or a course that has been approved by Profibus
International. The Installer shall submit a copy of their current Installation certification as proof.
Installers who are not certified but are involved in Profinet or Profibus installation work shall be
closely supervised and their work shall be checked by a certified installer.
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2
Profinet Design
2.1
Topology
Profinet supports a number of different topologies such as Line, Tree, MRP Ring and Star as well as
combinations of these.
The overall topology of the Profinet network is to a large extent pre-determined by the physical layout
of the Distributed Periphery (DP) within the Plant. There are nonetheless certain topology design
decisions to be made and care shall be taken to avoid impractical or inferior topology designs.
The topology design drawing shall include the following information:
• Estimated Network Load
• Update Times
Note: Either one Update Time value if it is the same for all I/O Devices OR individually specified per
device if different update times are used
• Device Names.
• IP addresses.
• Ethernet Cable length.
2.1.1
Line Topology (NOT to be used)
“Line Topology" is a misleading term for Profinet (or Ethernet Networks in general). While it may be
used by people to describe the look of Topology it does constitute a cascading of I/O devices via their
inbuilt switches as shown in Figure 1 below.
I/O
Controller
I/O
Device 1
I/O
Device 2
I/O
Device 3
I/O
Device 4
I/O
Device 5
I/O
Device 6
I/O
Device 7
Figure 1: Profinet Line Topology example
Points to note:
• The I/O Device’s inbuilt two-port switch is in essence a three-port switch (one internal and two
external ports) and the above line topology diagram is better represented as below
I/O
Controller
I/O
Device 1
I/O
Device 2
I/O
Device 3
I/O
Device 4
I/O
Device 5
I/O
Device 6
I/O
Device 7
Switch 1
Switch 2
Switch 3
Switch 4
Switch 5
Switch 6
Switch 7
Figure 2: Profinet Line Topology example detail
• Loss of downstream I/O Devices occurs if an upstream device is powered off.
• Loss of downstream I/O Devices occurs if the inbuilt switch of an upstream I/O Device fails.
Design rule:
• In consideration of the above shortcomings, Line Topology shall NOT be used.
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2.1.2
Star Topology
A Star Topology is created by simply using Network Switches with a number of devices connected to
them.
I/O
Controller
Switch
I/O
Device 1
I/O
Device 2
I/O
Device 3
I/O
Device 4
I/O
Device 5
I/O
Device 6
I/O
Device 7
Figure 3: Profinet Star Topology example
Points to note:
• Loss of the Switch means loss of all I/O devices connected to it.
Design rule:
• Star Topology (areas) become a natural part of any Profinet Network once Ethernet Switches
are in use.
• Star Topology may also be used by itself for smaller Networks, providing the following applies:
o
o
2.1.3
Only one Ethernet Switch is used.
I/O controller and I/O devices all reside in the same switch room.
Tree Topology (NOT to be used)
A combination of Line and Star and/or Multiple Star Topologies becomes a Tree Topology
I/O
Controller
Switch
Switch
I/O
Device 1
I/O
Device 2
Switch
I/O
Device 3
I/O
Device 4
Switch
I/O
Device 5
I/O
Device 6
I/O
Device 7
Figure 4: Profinet Tree Topology example 1 (multiple Star Topologies)
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I/O
Controller
Switch
I/O
Device 1
Switch
I/O
Device 2
I/O
Device 3
I/O
Device 4
Switch
I/O
Device 5
I/O
Device 6
I/O
Device 7
Figure 5: Profinet Tree Topology example 2 (Line and Star topology combined)
Design rule:
• Tree Topology shall NOT be used (MRP shall be used instead).
2.1.4
Media Redundancy Protocol (MRP) Ring Topology (to be used)
Network availability is increased by closing a Line Topology back to its starting point and thus
creating an MRP Ring
I/O
Controller
I/O
Device 1
I/O
Device 2
I/O
Device 3
I/O
Device 4
I/O
Device 5
I/O
Device 6
I/O
Device 7
MRP ring
Figure 6: Profinet I/O Controller/Devices inbuilt switches based MRP Ring Topology example
(information only, NOT to be used in the design)
The above topology utilises the inbuilt switch of each device and thus can only tolerate the powering
down of one I/O Device at a time.
For this reason, I/O Controller and I/O devices shall NOT be directly integrated into an MRP Ring via
their inbuilt Switch.
Dedicated switches shall be used instead as the backbone of the MRP Ring as shown in Figure 7
below.
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I/O
Controller
Switch
MRP Ring
Switch
I/O
Device 1
I/O
Device 2
Switch
I/O
Device 3
I/O
Device 4
Switch
I/O
Device 5
I/O
Device 6
I/O
Device 7
Figure 7: Profinet Switches based MRP Ring Topology example (MRP and Star combined)
Points to note:
• Whereas Profibus requires usage of OLMs to create a ring structure, Profinet MRP rings can be
based on Ethernet copper cables or fibre optic cables as well as a mixture of these.
• One switch in the ring acts as the MRP Ring Manager, all others act as MRP Clients.
• Ring reconfiguration time (e.g. due to cable break) can take up to 200ms. Therefore the
Watchdog time for ALL I/O Devices shall be set to a minimum of 200ms.
• A maximum of 50 Switches are allowed to be part of the ring.
• Using switches as the MRP backbone caters for connection of I/O Devices that have only one
physical Profinet port and/or don’t support MRP.
Design rules:
• If 2 (two) or more Ethernet Switches are part of the Network, MRP ring topology shall be used.
• The MRP ring shall only contain Ethernet Switches.
2.2
I/O Devices requirements
Only Conformance Class B compliant I/O Devices shall be used in the Design which ensures they
support the following as a minimum:
•
•
•
•
•
•
•
2.3
Cyclic I/O.
Acyclic Parameter data.
Device Diagnostics (Alarms).
Topology detection via LLDP.
Device identification via I&M (Information and Maintenance data).
Network diagnostics via SNMP.
Topology information via MIBs to enable SNMP readout.
Ethernet switches requirements
Only Conformance Class B compliant Ethernet Switches that additionally fulfil the following shall be
used in the Design:
• Managed Switch.
• Removable non-volatile storage medium that contains the switch configuration to cater for easy
Switch replacement.
• MRP support to cater for Ring Structures.
• QoS support to allow prioritisation of Profinet I/O telegrams.
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• I/O Device integration via GSDML file to allow integration of switches into the PLC
configuration.
2.4
Number of I/O Devices per Network
Whereas Profibus has a hard limit of 124 DP Slaves per DP Network, a Profinet Network can - at least
theoretically - contain thousands of I/O devices in one Network.
However, I/O Controllers (i.e. the PLC) impose limits on how many I/O Devices are supported. These
limits may vary greatly between different PLCs and Table 1 below contains for a few selected PLCs
and Gateways (valid as of December 2017 and subject to change for newer CPU versions and/or
firmware).
Note: At the time of writing Schneider Electric did not have a Profinet module for the M580 PLC.
Family
CPU
Supported number of I/O devices
Siemens
Profinet Interface of all CPUs
16 I/O devices
S7-1200
(as of firmware V3)
Siemens
1511-1 PN CPU
S7-1500
Profinet Interface
128 I/O devices
1515-2 PN CPU
Profinet Interface 1
256 I/O devices
Profinet Interface 2*
32 I/O devices
1518-4 PN/DP
Prosoft
Softing
Profinet Interface 1
512 I/O devices
Profinet Interface 2*
128 I/O devices
Communication module CM 542-1
128 I/O devices
EtherNet/IP to PROFINET
Controller Gateway PLX82-EIP-PNC
36 I/O devices
Modbus to PROFINET
Controller Gateway PLX82-MBTCPPNC
36 I/O devices
EtherNet/IP to PROFINET
Controller Gateway FG260
8 I/O devices
Table 1: S7 CPU examples for I/O Device capability
* These are to be confirmed by Siemens as it is not allowed in TIA Portal
The Designer shall check the limits of the CPU’s Profinet Interface(s) and/or Communication modules
and ensure the number of I/O Devices does not exceed 70% of its capacity to cater for future
expansion.
I/O Controller limit
70% rule Design Limit
16 I/O Devices
11 I/O Devices
32 I/O Devices
22 I/O Devices
64 I/O Devices
45 I/O Devices
128 I/O Devices
90 I/O Devices
256 I/O Devices
180 I/O Devices
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512 I/O Devices
200 I/O Devices (see note below)
Table 2: Profinet I/O devices 70% rule design limit
200 I/O Devices applies as the design limit for a Profinet Network even for I/O controllers that support
considerably more. PLCs that require more than 200 I/O Devices will need to comprise two or more
Profinet Networks (e.g. via usage of additional Profinet I/O Controller communication modules or a
second on-board I/O Controller interface).
NOTE:
Only I/O Devices that are directly connected to the Profinet Network count towards the 70%
rule design limit described in Table 2. PN/DP or PN/PA proxies count only as one I/O Device
each, irrespective of the number of underlying Profibus DP or PA devices.
However, subject to the chosen PN/DP or PN/PA proxy, the I/O Controller may include
underlying DP or PA devices in its overall I/O device count, thus imposing an engineering limit.
It is the designer’s responsibility to ascertain the functionality of any PN/DP, PN/PA or other
proxies to ensure the design complies with DS43-04 as well as the capabilities of the I/O
Controller.
2.5
Device Names
Each I/O Device shall be given a device name which shall be stated on the drawings (this is the
Profinet equivalent to the Node address as known from Profibus).
Device names shall in general comply with the IEC 61158-6-10 standard. For the purpose of this
Design Standard, the following rules shall be adhered to:
• A device name may be a maximum of 240 characters long and may only contain
o Lower case Letters.
o Numbers.
o Hyphen character (“-“).
o Period character (“.“).
• A device name shall start and end with a letter or number.
• A device name shall not have the form n.n.n.n (n = 0...999).
• A device name shall not start with the character string “port-xyz-“ (x,y,z = 0...9).
• Inside a device name, a string of characters between two periods forms a label which may not
exceed 63 characters.
• A label shall start and end with a letter or number.
Design Standard DS40-02 Naming Convention should be consulted for further detail.
2.6
IP addresses
IP addresses shall be allocated by Digital Services BU by means of an LTM/PTM request submitted to
the Design Manager or Project Manager by the Designer
I/O Controller (PLC) and each I/O device shall have an IP address which shall be stated on the
drawings.
Note that CPUs with multiple onboard Profinet Interfaces require to have its own IP address range for
each onboard Profinet Interface, for example (255.255.255.0 assumed as the Subnet mask):
• 192.168.0.0 to 192.168.0.255 for the first onboard Interface.
• 192.168.1.0 to 192.168.1.255 for the second onboard Interface.
While usage of additional Profinet I/O controller cards in the CPU rack may allow re-using the same
IP address range, this shall be avoided.
Design rule:
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• Each Profinet network shall have its own IP address range.
2.7
Update Times
Unlike Profibus, each Profinet I/O Device can have its own update time.
Profinet RT I/O update times can be set in multiples of 2 with 1 ms being the fastest.
Note that Update Times have a direct impact on Network load, Table 3 below contains a list of
recommended update times based on number of devices.
I/O update times
(ms)
Notes
NOT to be used unless specific process requirements exist that
require it
NOT to be used unless specific process requirements exist that
2
require it
NOT to be used unless specific process requirements exist that
4
require it
NOT to be used unless specific process requirements exist that
8
require it
Recommended for all Networks
16
Avoid unless required to keep Network load down
32
Avoid unless required to keep Network load down
64
May also be used for wireless I/O devices
To be used for managed Ethernet switches (their I/O is purely for
diagnostics purposes and NOT time critical).
128
May be used for wireless I/O devices
Avoid
256
May be used for wireless I/O devices if 128ms is too fast for them
NOT to be used
512
Table 3: Profinet update times selection table
1
2.8
Network load
Due to the switched nature of the Profinet Network, Network load varies across different parts of the
Network and also depends on the topology. The I/O Controller will in general though experience the
highest Network load of Profinet RT I/O traffic.
Two examples below show the effect topology has on network loading per individual port to port
connection, values used for these examples are:
• Update time: 1ms for all I/O devices
• I/O Device:
I/O
Controller
4.9%
Card Type
32 Digital Inputs
32 Digital Inputs
8 Analogue Inputs
32 Digital Outputs
32 Digital Outputs
8 Analogue Outputs
I/O
Device 1
4.2%
I/O
Device 2
I/O
Device 3
3.5%
2.8%
Bytes
4
4
16
4
4
16
I/O
Device 4
I/O Bytes Totals
24
24
I/O
Device 5
2.1%
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I/O
Device 6
I/O
Device 7
0.7%
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Figure 8: Line Topology Network Load example (1ms update time, 24 Bytes Inputs and Outputs per
I/O device)
I/O
Controller
4.9%
Switch
0.7%
I/O
Device 1
I/O
Device 2
0.7%
0.7%
I/O
Device 3
0.7%
0.7%
I/O
Device 4
0.7%
I/O
Device 5
0.7%
I/O
Device 6
I/O
Device 7
Figure 9: Star Topology Network Load example (1ms update time, 24 Bytes Inputs and Outputs per
I/O device)
Table 4 below contains an overview of Network Load results in relation to number of I/O Devices and
Update time (each I/O Device comprising of 24 Bytes of Inputs and 24 Bytes of Outputs).
Green highlighted cells indicate the Network load for the recommended 16ms Update times.
Network Load (%)
25
50
100
150
200
250
Devices
Devices
Devices
Devices
Devices
Devices
1
17.6
35.2
70.4
105.6
140.8
176.0
2
8.8
17.6
35.2
52.8
70.4
88.0
4
4.4
8.8
17.6
26.4
35.2
44.0
8
2.2
4.4
8.8
13.2
17.6
22.0
16
1.1
2.2
4.4
6.6
8.8
11.0
32
0.55
1.1
2.2
3.3
4.4
5.5
Table 4: Network Load examples (24 Bytes of Inputs and 24 Bytes of Outputs per I/O Device)
Update Time
(ms)
The expected Network load shall be calculated.
PI’s Network load calculation Excel sheet shall be used for this purpose with an averaged I/O amount
per Device to perform a simplified Network load calculation.
While the calculation Excel sheet contains instructions on how to use it, the following applies for the
purpose of a standardised rule of thumb calculation:
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Figure 10: Network load calculation tool usage example
1.)
2.)
3.)
4.)
Minimum transmit clock:
Number of devices:
Number of modules:
Net data per device:
5.) Update time per device group:
6.) Common Network load:
Always use 1 ms
Count of all I/O Devices on the Network, excluding Switches
Set to 3 for Input and Output
Input: Roundup (Sum of all Input Bytes/Number of device)
Output: Roundup (Sum of all Output Bytes/Number of devices).
Set to the recommend 16ms for Input and Output (unless other
update times are required or desired).
Result of calculation, value is displayed in Mbit/s which is
equal to % as Profinet operates on a 100Mbit/s Network.
Full duplex operation means the higher of the two values is the
worst one.
Other Notes:
• Ignore “drives” Group 4 to 6 and include Drives in the general “Remote I/O” Goup 1
• Group 2 and Group 3 only need to be used if Devices with different update times are on the
Network.
Design rules:
• Profinet RT I/O traffic shall be kept below 25% (25MBits/s)
• Total Network load shall not exceed 50% (50MBits/s)
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2.9
SCADA and OIP connections
SCADA system shall be connected to the PLC via a separate Ethernet Network and shall NOT be
connected to the Profinet Network.
Connection to the PLC can either be done via a dedicated Ethernet card in the PLC rack or via a
second on-board CPU Ethernet interface that is NOT part of a Profinet Network.
OIPS may be connected directly to the Profinet Network providing the following applies:
• they communicate directly with the control system (i.e. they are NOT SCADA Clients) and
• they are located in the field without easy access to the SCADA Ethernet Network
SCADA
SCADA
SCADA Ethernet Network
I/O
Controller ETH
Switch
MRP Fibre Optic Ring
Switch
Switch
I/O
I/O
I/O
I/O
I/O
Switch
I/O
I/O
I/O
I/O
I/O
I/O
OIP
Figure 11: Example SCADA and OIP connection
2.10
Number of I/O Controllers per Profinet Network
Designers may be tempted to design one large fibre optic MRP ring and have multiple I/O Controllers
and all I/O Devices connected to one Profinet Network as per example Figure 12 below.
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SCADA
SCADA
SCADA Ethernet Network
I/O
Controller ETH
I/O
Controller ETH
Switch
Switch
MRP Fibre Optic Ring
Switch
Switch
I/O
I/O
I/O
I/O
I/O
Switch
I/O
I/O
I/O
I/O
Switch
I/O
I/O
I/O
I/O
I/O
I/O
OIP
Figure 12: NOT allowed - multiple PLCs on one Profinet Network
While the above will technically work, it creates the following issues:
•
•
•
•
Creation of larger than required Profinet Networks.
Network load not easily estimated and requires usage of specialised tools (e.g. SINETPLAN).
All Devices share the same IP address space.
Assignments of which I/O Device belongs to what I/O Controller is no longer easily ascertained
from the schematics.
• I/O devices belonging to different I/O Controllers may end up being connected to the same
switch, a switch failure (or wilful isolation of an area) now leads to two or more I/O
Controllers losing I/O devices.
Design rule:
In consideration of the above shortcomings, there shall be no more than 1 (one) Profinet I/O Controller
connected to a Profinet Network.
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SCADA
SCADA
SCADA Ethernet Network
I/O
Controller ETH
I/O
Controller ETH
Switch
MRP Fibre Optic Ring
Switch
Switch
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
Switch
Switch
I/O
I/O
I/O
I/O
I/O
I/O
I/O
OIP
Figure 13: Allowed - each PLC with its own Profinet Network
2.11
Inter PLC communication
PLC to PLC communication can be achieved via the common SCADA Network or via PN/PN
couplers.
2.12
Siemens S7 H-Systems
Should the design call for redundant CPUs in the form of a Siemens S7-400 H System, the following
additional requirements shall apply (Note: the S7-400H is due to be replaced by the CPU1513R,
CPU1515R and CPU1517H late in 2018):
• MRP is NOT to be used as the main backbone.
S7-400 H systems employ either “Open Ring” Topology OR redundant Profinet Networks instead.
• If “Open Ring” Topology is used, I/O Devices shall support System redundancy (also referred
to as “S2” in Siemens speak). This allows the I/O Device to maintain an Application and
Communication relationship with both CPUs and carry out a bump-less switch over from one
CPU to the other in case of CPU failures.
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CPU “A”
FO sync. link
CPU “B”
“Open Ring”
Switch
Switch
I/O
I/O
I/O
I/O
I/O
Switch
I/O
I/O
I/O
I/O
I/O
I/O
EACH I/O device MUST support
System redundancy
I/O
Figure 14: S7-400 H System "Open Ring" Profinet Network example
• If redundant Profinet Networks are used to further increase the availability of the Network, I/O
devices shall be equipped with redundant Interfaces (also referred to as “R1” in Siemens
speak).
CPU “A”
Switch
FO sync. link
CPU “B”
Switch
I/O
I/O device with
redundant Interface
I/O
I/O device with
redundant Interface
I/O
I/O device with
redundant Interface
I/O
I/O device with
redundant Interface
Figure 15: S7-400 H System with redundant Profinet Networks example
The connection of I/O devices without redundant Interface to a redundant Profinet Network is possible
via usage of so called “Y Switches”.
Note that the I/O Device shall still support System redundancy.
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CPU “A”
FO sync. link
CPU “B”
Switch
Switch
I/O
I/O device with
redundant Interface
I/O
I/O device with
redundant Interface
I/O
I/O device with
redundant Interface
Y
I/O
I/O device without redundant Interface
(MUST support System redundancy)
Y Switch
Figure 16 S7-400 H System with redundant Profinet Networks with “Y” switch
2.13
Device Certification
Device certification is mandatory for all Profinet I/O Devices and I/O Controllers thus ensuring that
only certified devices are being used.
2.14
Cable and Connector Specification
Shielded CAT5 cable shall be used as the minimum standard (i.e. Industrial Ethernet cable).
Shielded CAT5e or CAT6 cable may also be used.
Only shielded RJ45 connectors shall be used.
Fast Connect cable and connectors shall be used (refer 5.4).
2.15
Cable length
The design cable length of copper based Ethernet cables shall not exceed 80 meters.
Copper based Ethernet cable length shall be shown on the drawings.
2.16
Integration of Profibus PA devices
Integration of Profibus PA devices take place via PN/PA proxies who cater for the transition from
Profinet to Profibus PA as per example in Figure 16 below
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I/O
Controller
Switch
I/O
Device
PN/PA
Proxy
T
I/O
Device
I/O
Device
I/O
Device
I/O
Device
Junction
Box
PA
Slave
Junction
Box
PA
Slave
PA
Slave
I/O
Device
PA
Slave
PA
Slave
PA
Slave
T
PA
Slave
PA
Slave
Figure 17: PN/PA Proxy usage example
Points to note:
• Capabilities of PN/PA Proxies vary greatly between manufacturers. It is the Designer’s
responsibility to check the PN/PA Proxy’s datasheet to ensure the limitations are adhered to
and the required spare capacity exists.
• PN/PA Proxy manufacturers generally cater for vendor neutral GSDML file based integration of
the Proxy.
• Siemens “SIMATIC CFU PA” (6ES7655-5PX11-0XX0) can only be used with S7 PLCs as the
I/O Controller (S7-300, S7-400 and S7-1500).
2.17
Integration of Profibus DP Slave devices
Usage of Profibus DP Slaves is to be avoided unless:
• A Device that is mandated to be used is not available with a Profinet I/O Device interface
• It is for a brown-field site PLC upgrade where existing Profibus DP Slave devices need to be
integrated
If integration of DP Slaves is required, PN/DP Proxies are employed for the transition from Profinet to
Profibus DP as per example in Figure 17 below:
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I/O
Controller
Switch
I/O
Device
(PN/DP
Proxy)
T
I/O
Device
I/O
Device
DP
Slave
DP
Slave
I/O
Device
DP
Slave
I/O
Device
DP
Slave
I/O
Device
AT
Figure 18: PN/DP Proxy usage example
Points to note:
• PN/DP Proxy manufacturers generally cater for vendor neutral GSDML file based integration of
the Proxy.
• Siemens PN/DP proxy (part number 6GK1411-5AB10) can only be used with Siemens S7 PLCs
as the I/O Controller (S7-300, S7-400 and S7-1500).
• It is the Designer’s responsibility to check the PN/DP Proxy’s datasheet to ensure the
limitations are adhered to and required spare capacity exists.
Key differences between Siemens and GSDML file based PN/DP proxies are listed in Table 5 below.
Manufacturer/
Type
Siemens “IE/PB LINK PN IO”
(6GK1411-5AB10)
GSDML file based PN/DP Proxy
Proxy functionality
Semi-transparent
Each DP Slave counts towards the
number of configured I/O
devices.
Not transparent
Proxy counts as one I/O Device
irrespective of the number of
underlying DP Slaves.
Underlying DP Slaves are presented
as I/O modules inside the Proxy.
Can be used with any No (only useable with Siemens S7
PLCs)
I/O Controller?
Number of DP Slaves
65
behind one Proxy
Amount of I/O per
2048 Bytes
Proxy
Other
Easy integration into Siemens S7
based control systems
Yes
Depends on chosen Proxy, check
datasheet
Depends on chosen Proxy, check
datasheet (but never more than 1440
Bytes)
Profinet GSDML I/O device file
shall be created via proxy
manufacturer supplied engineering
tool
Table 5: PN/DP Proxies differences
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Design Standard No. DS 43-04
Profinet and Profibus Network Design and Installation
2.18
Designer Checklist
The following checklist shall be used to ensure that the Profinet design meets the requirements of this
standard. The answer shall be “Yes” to all the questions.
Chapter
Criteria
2.1.1
Line Topology is NOT used?
2.1.3
Tree Topology is NOT used?
2.1.4
MRP backbone is used if more than 1 (one) Switch is in the Network?
2.1.4
If MRP is used, only Ethernet switches are part of the ring?
2.2
Only Conformance Class B compliant I/O Devices are used?
2.3
Only compliant Ethernet Switches are used?
2.4
Number of I/O Devices per Network does not exceed the 70% rule?
2.4
Number of I/O Devices per Network does not exceed 200?
2.5
Drawings show Device Names?
2.6
Drawings show Devices IP addresses?
2.6
Each Profinet Network has its own IP address range?
2.7
Drawings stipulate the Update Times?
2.8
Estimated Network Load is <=25%?
2.8
Estimated Network Load is shown on drawings?
2.9
SCADA is connected separately to the Profinet Network?
2.10
Only one I/O Controller per Network?
2.15
Ethernet copper cable runs are <=80 meters?
2.15
Ethernet copper cable run lengths are shown on drawings?
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3
Profibus DP Design
3.1
Topology
Profibus DP does generally support a number of different topologies such as (linear) bus, tree,
(redundant) ring and star as well as combinations of these.
The overall topology of the Profibus network is to a certain extent pre-determined by the physical
layout of the distributed periphery within the Plant. There are nonetheless certain topology design
decisions to be made and care shall be taken to avoid impractical or inferior topology designs.
The topology design drawing shall include the following information:
-
Estimated cable length for each cable run.
Bus speed.
Termination requirements.
Node addresses.
Estimated DP cycle time.
The copper segments of a Profibus-DP network shall be a linear, multi-drop network.
Copper Profibus-DP sections shall obey the same rules as the RS-485 system on which it is based.
3.1.1
Fibre optic
Fibre Optic cabling may be required for certain parts of overall Profibus network for example due to
requirements for extended outdoor cable runs (see DS 43-06 for more on this).
Permissible Fibre Optic topologies are:
- Linear bus (also known as “Line”).
- (Redundant) ring.
- Star.
The following shall be noted and considered when designing the fibre optic topology:
- Preference should be given to using the redundant ring topology in cases where two or more
fibre runs are involved (i.e. three or more OLMs are linked together via fibre optic cable). The
advantages that ring redundancy offers outweigh the extra costs for the extra fibre run required
to convert from line to ring. An exception to this rule is where a number of OLMs are used in
line to be able to span greater distances.
- The three possible fibre optic topologies should be treated as mutually exclusive and should not
be “mixed and matched” within one Profibus network unless specific reason exists in which
case the matter shall be referred to the Principal SCADA Engineer.
- The maximum bridgeable distances between two OLMs is an ideal maximum and only valid for
uncut lines without any optical couplings. An optical power budget calculation should be done
to calculate and verify the system reserve for any fibre runs which exceed half of the
maximum bridgeable distances between two OLMs.
o
Example: Siemens Glass multimode OLM (e.g. type G11 or G12) allow for up to 3
kmS between two OLMs. An optical power budget calculation is only required with
these OLMs for fibre cable length of more than 1.5 km between two OLMs.
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- Each OLM causes a slight delay (~ 6 tBit) in the transmission of the Profibus message due to the
required signal conversion. This may need to be taken into account when calculating the bus
parameters unless the configuration software allows for inclusion of the number of OLMs and
fibre cable length in its calculation.
3.1.1.1
Fibre Optic Linear bus (Line) Topology
Fibre Optic Line
OLM
OLM
OLM
DP
Slave
DP
Slave
DP
Slave
DP
Slave
RS 485
DP
Slave
DP
Master
Fibre Optic
DP
Slave
Figure 19 Example Fibre Optic Line Topology
(Note: RS485 Termination requirements not shown)
Points to note:
- None
3.1.1.2
Fibre Optic (redundant) Ring Topology
(redundant) Fibre Optic Ring
OLM
DP
Slave
OLM
OLM
DP
Master
DP
Slave
OLM
DP
Slave
DP
Slave
RS 485
DP
Slave
DP
Slave
Fibre Optic
DP
Slave
Figure 20 Example Fibre Optic Ring Topology
(Note: RS485 Termination requirements not shown)
Points to note:
- Due to the OLM inbuilt automatic monitoring functionality and self healing nature of the ring,
the Profibus bus timings and setup (i.e. Highest station address, Slot time, Min TSDR and
Retry value) shall be adjusted in accordance with the OLM manual (Note: Some Profibus
configuration software packages have OLM/fibre based topologies configuration included and
are able to automatically calculate and adjust the bus parameters accordingly).
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Profinet and Profibus Network Design and Installation
3.1.1.3
Fibre Optic Star Topology
RS 485 Star
Segment!
OLM
OLM
RS 485
OLM
Fibre Optic “Star”
OLM
OLM
DP
Slave
DP
Slave
Fibre Optic
OLM
OLM
OLM
DP
Slave
OLM
DP
Slave
DP
Slave
DP
Master
DP
Slave
DP
Slave
Figure 21 Example Fibre Optic Star Topology
(Note: RS485 Termination requirements not shown)
Points to note:
- The OLMs are linked together via their RS485 ports to create a (hub like) Star coupler. The
small but important RS485 star segment now becomes the main backbone of the whole
Profibus network (whereas the fibre is the backbone of the Profibus network in a redundant
ring configuration)!
- The RS485 Star segment shall be carefully wired and kept as short as possible (NOTE: The rule
of a minimum of 1 meter cable between two adjacent devices shall still be complied with).
- Connection of any other bus participants (e.g. Masters, Slaves) to the RS485 Star segment
should be avoided altogether.
- Segment monitoring of the RS 485 channel should be turned off on each of the Star coupler
OLMs to keep up a high availability of the RS485 Star segment and therefore of the whole
network.
For these reasons, Fibre Optic Star Topologies should be avoided altogether unless specific design
criteria exist in which case the matter shall be referred to the Principal SCADA Engineer.
3.1.2
RS 485 (copper)
Permissible RS 485 topologies are:
- Linear bus (Line).
- Tree.
The following shall be noted and considered when designing the RS 485 bus segments:
-
Number of devices per RS 485 Segment.
RS 485 Segment cable length/desired Bus speed.
Termination.
Minimum of 1 meter cable between nodes.
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3.1.2.1
RS 485 Linear bus (Line) Topology
AT
DP
Master
DP
Slave
DP
Slave
DP
Slave
DP
Slave
AT
AT Active Terminating Resistor
T Termination activated on Device or Plug
Figure 22: Example RS 485 Line Topology
Points to note:
- None
3.1.2.2
RS 485 Tree Topology
AT
DP
Master
DP
Slave
DP
Slave
DP
Slave
DP
Slave
AT
DP
Slave
Repeater
AT
Repeater
AT
DP
Slave
T
AT Active Terminating Resistor
T Termination activated on Device or Plug
AT
DP
Slave
DP
Slave
Figure 23: Example RS 485 Tree Topology
Note: The cascading depth of repeaters (i.e. permissible number of repeaters downstream of each
other) is limited and depends on the type of repeater (e.g. 9 in case of Siemens repeaters).
3.2
Number of Devices per RS 485 Segment
It is generally permissible to connect up 32 devices to a single RS 485 segment. In practice this should
be avoided though as it leaves no “space” for the temporary connection of diagnostics or
troubleshooting tools to the segment. Furthermore, any additional devices required to be added in the
future half way though the segment would require additional repeaters somewhere in the field or a
redesign of the segment.
The 20% spare capacity rule is to be applied to the number of devices per RS 485 segment and no
more than 26 devices shall be foreseen per Segment in the original design.
For ease of troubleshooting and maintenance related tasks, only “Piggyback” Profibus Plug shall be
used for devices with a DB9 Plug connection.
In principal all devices which do have an RS 485 interface (driver chip set) shall be counted as a
“device” irrespective if they have node address and participate in the bus communication or not.
The following is a list of Profibus items that shall be included in the device count on the RS 485
segment:
- DP Masters (e.g. PLCs, PCs).
- DP Slaves (e.g. I/O stations, Valves, Instruments).
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-
Diagnostic tools (e.g. Profitrace).
Repeaters (incl. Diagnostic Repeaters).
OLMs.
DP/DP couplers.
DP/PA links.
DP/PA couplers (Only if directly connected to the DP bus, not if located behind a DP/PA link)
Surge Arrestors (even though they are passive devices without an RS 485 driver chip interface,
their capacitive mismatch influences the signal quality).
Profibus items which do NOT count as a “device”:
- Active terminating resistors
- Profibus Plugs on a device (irrespective if termination is activated on them or not)
3.3
Node Addresses
The following Node address assignment rules apply:
Address
Device
0
Not to be used (reserved for the connection of temporary Class 2 master diagnostic tools)
1
Main DP Master (Main PLC)
Additional Masters
2…n
n…125
(nminimum = 10)
(i.e. other DP Master PLCs, HMI stations, permanently installed Device Manager PCS or Class 2 Master Diagnostic
stations etc.)
DP Slaves
(Note: Use 10 as the minimum address)
Table 6: DP Node address assignment
DP Slave address numbers shall - where possible - be assigned with consideration to their associated
Plant area.
Example Node Address assignment for a Water treatment Plant with 8 Filters:
Each Filter has 6 associated Profibus DP Slaves associated with it (e.g. one general I/O Station, one
Flow meter with DP interface and 4 Valves with DP interface).
Similarly to the Instrument number reflecting the associated Filter number, the DP Slave addresses
may, as an example, be logically allocated as follows:
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Profinet and Profibus Network Design and Installation
Address
Device
0
Free
1
Main PLC
2…n
Reserved
10-15
Filter 1 Slaves (16-19 reserved for Filter 1)
20-25
Filter 2 Slaves (26-29 reserved for Filter 2)
30-35
Filter 3 Slaves (36-39 reserved for Filter 3)
40-45
Filter 4 Slaves (46-49 reserved for Filter 4)
50-55
Filter 5 Slaves(56-59 reserved for Filter 5)
60-65
Filter 6 Slaves (66-69 reserved for Filter 6)
70-75
Filter 7 Slaves (76-79 reserved for Filter 7)
80-85
Filter 8 Slaves (86-89 reserved for Filter 8)
90-109
Not used (deliberately kept free for future Filters)
110-125
Remaining other Plant general Profibus DP Slaves
Table 7 DP Slave Addresses
3.4
Number of Nodes on a Profibus network
A distinction is made between the total number of Nodes on the Profibus network versus the number
of devices per individual RS 485 segment.
Every device that participates in the communication and does have a Node address (i.e. Masters and
Slaves) is to be taken into account for this.
The following is a list of Profibus devices that require a Profibus address and shall be included in the
Node count on the network:
-
DP Masters (e.g. PLCs, PCs)
DP Slaves (e.g. I/O stations, Valves, Instruments)
Diagnostic Repeaters
DP/DP couplers
DP/PA links
A single Profibus network is in principle capable of containing a total of 126 Nodes (Address range 0
to 125) across several RS 485 segments. Since address 0 is not to be used, a maximum of 124 DP
Slaves could in theory be connected to the Master port of the PLC (and if the PLC has more DPMaster ports, each is again capable of containing another 124 Nodes).
Designs with more than 80 DP-Slaves on a single Profibus Network are be avoided in order to keep
the bus cycle time at an acceptable level (see 3.5 below for more on this).
3.5
Bus cycle time
To determine the feasibility of the Profibus Network design with regards to the bus cycle time, the
designer shall take into account the total number of nodes, the amount of I/O data that is to be
exchanged and the bus speed.
For any given bus speed, there is a linear relationship between the number of DP-Slaves on the bus,
their I/O count and the bus cycle time (i.e. the more Slaves and/or the more I/O bytes per Slave, the
longer it takes to complete a bus scan and refresh all inputs and outputs).
The (simplified) formula to calculate the typical bus cycle time in a Mono-Master Profibus DP
network is:
Equation 1: Typical DP cycle time equation (Mono-Master system)
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𝐷𝐷𝐷𝐷t =
380 + 300 ∗ NDPS + BitDP ∗ TIOB
Bsd
+ 0.000075𝑠𝑠
NDPS: Number of DP Slaves (eg 20)
BitDP: Bits per DP Byte (constant: 11 bit/byte)
TIOB: Total of all Input and Output Bytes (eg 496)
Bsd: Bus Speed (in bits per second)
Formula courtesy of Andy Verwer (MMU PROFIBUS Competence Centre)
Note: the above formula assumes an averaged amount of I/O data per Slave (and as such it also
assumes that every Slave has input & outputs). It nonetheless provides a good enough indication of the
expected typical bus cycle time when operated in normal cyclic I/O data exchange. The number of
repeaters or OLMs, Bus retries, or diagnostic data messages etc. are not taken into account.
Even though Water related process control systems typically do not have any high speed I/O reaction
or bus cycle time requirements, the following rules apply:
1. The calculated typical bus cycle time shall be able to accommodate the fastest changing
input signals.
One example would be flow meter count pulses. If litre pulses are required to be counted at a
maximum flow of 10 litres/second, the input would change state every 50 ms at maximum flow. This
would require a typical bus cycle time well below 50ms to avoid that pulses can go undetected (which
in turn would lead to falsified results of the PLC based totaliser count). Alternative arrangements shall
be sought in this case for the affected inputs (e.g. wired back to an Input card in the central rack, usage
of high speed counter cards etc.).
2. The calculated typical bus cycle time shall not exceed 100ms. If this can’t be avoided the
matter shall be referred to the Principal SCADA Engineer.
Profibus Master configuration tools (e.g. Siemens Step 7) will calculate the typical bus cycle time
automatically for any given configuration and may also be used to estimate it.
If PA devices are part of the overall Profibus network, their impact on the DP bus cycle time depends
on the type of DP/PA link used.
- Siemens DP/PA Link: The Siemens DP/PA link is a DP Slave which holds and buffers all the
values of the underlying PA Slaves (up to 244 Bytes of I/O per DP/PA link). It is simply to be
added to the above formula as ONE DP Slave with an I/O count comprising of the sum total of
each connected PA Slave.
- P&F DP/PA Gateway: P&F DP/PA Gateway is transparent for the DP Master who treats each
PA Slave just like a DP Slave. Each PA Slave with its respective I/O count is as such to be
included into the above formula. Note that the Gateway itself is also a DP Slave with 1 Byte
I/O.
3.6
Bus speed & Segment Cable Length
Profibus offers the choice of 10 different baud rates. The baud rate also determines the maximum
permissible RS485 segment length; their relationship is shown in the table below:
Table 8: Profibus DP Maximum Segment length versus Baud rate
Baud rate (Kbit/s)
Segment Length (m)
9.6
19.2
45.45
93.75
187.5
500
1500
3000
6000
12000
1000
1000
1000
1000
1000
400
200
100
100
100
Note 1: The Profibus Standard allows 1200m, this has however been limited to 1000m for the purpose
of this Standard
Note 2: These lengths are defined for Segments with 32 Devices attached to it.
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1500 Kbit/s is the preferred baud rate and the Profibus design should accommodate this baud rate.
500 Kbit/s may be chosen as an alternative (note the bus cycle time impact). This alternative shall
however be submitted to the Principal SCADA Engineer for approval.
The design shall show the estimated cable length for each Device and Segment.
Baud rates higher than 1500 Kbit/s are not necessarily supported by all DP Slaves and also require
extra care with auxiliary equipment selection. They should be avoided unless specific reasons exists
(i.e. Bus cycle time requirements) which warrant its usage.
3.7
Spurlines
Spurlines are caused by branches of the main DP bus line and shall NOT be deliberately included in
either the design or implementation.
Bus Cable
T-Tap or
Junction Box
Bus Cable
Spur
DP
Slave
DP
Slave
Figure 24: Spurline example
Figure 25: Typical “loop through” connection
Points to note:
- The end of a Spurline shall NOT be terminated.
- Spurlines cause problems due to their capacitive influence. Additional devices in the spurline
like surge arrestors have a compounding affect and their capacitance shall be taken into
account.
Since Spurlines shall not be deliberately included in either the design or implementation, the
allowance shown in Table 8 below is to be used only to verify the design which includes equipment
with known internal spurlines.
Table 9: Maximum permissible TOTAL Spurline length per Segment versus baud rate
Baud rate (Kbit/s)
9.6
19.2
45.45
93.75
187.5
500
1500
3000
6000
12000
Max. TOTAL Spurline Length per
Segment (m)
500
500
100
100
33
20
6.6
0!
0!
0!
Max. TOTAL Capacity of Spurs
(nF)
15
15
3
3
1
0.6
0.2
0
0
0
Note: The maximum total capacitance of the spur is the same as the maximum total spurline length if
type A Profibus cable is used (with <30pF/m).
There may be cases where the “loop through” connection is not feasible to avoid a spurline. This could
be due to long cable runs out to an individual device in combination with surge arrestor requirements.
A different method to overcome this problem is the usage of a repeater as shown in Figure 25 below.
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Bus Cable
Repeater
T
T
DP
Slave
Figure 26: DP Repeater usage to avoid spurlines
In this case the repeater creates a complete new RS485 segment, capable of handling up to 31 devices
(it is NOT a spurline, note also the termination requirements).
If a number of devices require repeater based connections, the costs aspect of one repeater per device
becomes uneconomical (on top of installation and space requirements). In this case devices known as
“Repeater Hubs” are to be employed instead. These “Repeater Hubs” are what the name suggests, a
number of repeaters bundled inside a single device.
Bus Cable
Repeater Hub
T
DP
Slave
T
T
T
T
T
T
T
DP
Slave
DP
Slave
DP
Slave
T
DP
Slave
DP
Slave
AT
Figure 27: DP Repeater Hub usage example
Just like repeaters, each newly created segment that branches of the hub is a fully fledged RS 485
segment, capable of handling up to 31 devices.
3.8
Termination
Each RS 485 segment requires active termination on either end of the segment (active termination
refers to the fact that +5V is required to power the termination).
+ 5V
390 Ω
B Line
220 Ω
A Line
390 Ω
GND
Pin 6 D
B
9
Pin 3 C
o
n
n
Pin 8 e
c
t
o
Pin 5 r
Figure 28: Profibus DP termination structure and DB9 connector pin assignment.
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It is mandatory for a device with a DB9 Connector to comply with the above Pin layout and provide
the 5V as well as ground connection. Most DB9 Profibus Plugs have a switchable termination resistor
combination inbuilt and as such allow termination via the Plug.
Devices without DB9 connector (e.g. terminal connection, M12 plugs) will typically have switchable
termination resistors inbuilt. This shall however be verified in case the device is to be the first or last
in the segment.
Note that removal of a DB9 connector with switched on termination in the Plug from a device will
lead to a loss of proper segment termination as it removes the 5V as well as the Ground connection
and leaves only the 220 Ω between B and A line! Note further that powering off a device at the start or
end of the segment will also lead to a loss of proper segment termination!
To overcome the associated risk of upsetting the whole RS 485 segment, external active termination
resistors are to be installed if any of the following is true:
- The Segment contains more than 1 DP Slave.
- The Segment contains more than 2 Devices with RS485 interface.
- In addition, an active terminator shall always be used at the PLC end to aid with the connection
of troubleshooting tools without the need to touch the CPU.
Devices where it is permissible to use inbuilt or DB9 Plug terminations are:
OLMs (in cases where only Slaves are connected on their RS 485 port)
- Repeaters (in cases where only Slaves are connected to the port which creates the new Segment.
See also “Notes 1 and 2” in Figure 29 below as an example for this).
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AT
DP
Master
DP
Slave
AT
DP
Master
DP
Slave
DP
Slave
T
T
NOT ok.
More than 1 DP Slave on one
Segment. Active terminating resistor
must be used.
AT Active Terminating Resistor
T Termination activated on Device or Plug
NOTE 2:
Active terminating resistor required to
maintain integrity of this Segment in
case of repeater failure
AT
DP
Master
DP
Slave
DP
Slave
AT
NOT ok.
More than 2 Devices with RS 485
interface on one Segment. Active
terminating resistor must be used.
AT
DP
Slave
DP
Master
T
Repeater
T
DP
Slave
Repeater
T
T
DP
Slave
T
DP
Slave
NOT ok.
More than 1 DP Slave on one
Segment. Active terminating resistor
must be used.
NOTE 1:
OK, if repeater or power to it fails, this
segment will be “lost” anyhow.
(Repeater is treated like a DP Master
at Segment start in this case).
Figure 29: Correct and incorrect DP Segment termination examples
3.9
Certification
Designers shall ensure that Profibus Master and Slave devices are certified by a Profibus International
approved test laboratory. The Designer shall submit to the Water Corporation a copy of the valid and
current certificates for these devices at the time of submitting the Topology drawings for the Water
Corporation’s comment.
Device certification gives the user assurance that the device complies with the Profibus specifications
and only certified Profibus Masters and Slaves shall be used in the design. Devices (Masters and
Slaves) from manufacturers who are unable to supply current and valid certificates for their devices by
a Profibus International approved test laboratory shall not be used in the design.
Note that Profibus device certification is only available for Master and Slave devices. Standard
Repeaters, OLMs, Plugs or other Profibus items that are neither Master nor Slave are not certifiable
(The DP Slave interface functionality of Diagnostic Repeaters or DP/DP couplers for example can be
certified though).
3.10
Cable specification
DP Cable type A shall be used for all Profibus DP RS485 cables which has the following
characteristics:
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Parameter
Value
Cable design
Twisted pair, shielded
Impedance
150 Ω +/- 15 Ω (at 3 to 20Mhz)
Capacitance
< 30pF/m
Loop resistance
< 110 Ω/km
Wire diameter
> 0.64 mm
Core cross section
> 0.32 mm2
Table 10: DP cable type A specification
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4
Profibus PA Design
4.1
Topology
Profibus PA supports tree and linear bus topologies. Unlike DP, connection of PA devices to the bus is
typically done via spurlines, which either branch of dedicated junction boxes or individual “T” taps.
Note that the 2 wire bus does also serve to supply power to the PA devices.
The topology design drawing shall include the following information:
-
Estimated cable length for each cable run.
Termination requirements.
Node addresses.
Current consumption and Voltage drop per PA Segment.
Estimated PA cycle time.
PA Device Manager Station (configuration, maintenance, diagnosis …)
PA
Slave
PA
Slave
Plant Ethernet network
DP
Master
Gateway
PA
Slave
PA
Slave
PA
Slave
DP network
DP/PA
Link/
Couplers
T
PA “Trunk”
Junction
Box
“T”
Tap
“T”
Tap
Junction
Box
T
PA
Slave
24V
PA
Slave
PA
Slave
PA
Slave
PA
Slave
PA
Slave
PA
Slave
Note: Each PA spurline is assumed to
be <= 90m in this example.
PA
Slave
PA
Slave
Figure 30: Typical PA Topology example including termination requirements & Device Manager
Station
4.2
DP/PA Link and Coupler selection
There are in principal the following two different ways to link a (Manchester bus powered) PA
network to a (RS 485) DP network:
1. Directly via PA couplers (NOT TO BE USED)
2. Indirectly via PA couplers behind a DP/PA link (TO BE USED)
Item 1 requires the DP network to operate at reduced baud rates (45.45 for Siemens PA couplers and
93.75 Kbit/s for P&F Segment couplers). PA couplers shall not be directly connected to a DP
network and the associated design requirements for direct PA coupler connection to a DP
segment will not be further discussed.
This leaves item 2 and the designer is faced with making the choice between a Siemens or a Pepperl &
Fuchs or a PROCENTEC based solution.
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Siemens, P&F and PROCENTEC employ different strategies concerning the functionality of their DP/PA link/coupler combination. The general differences are
outlined in the selection Table 10 below.
Table 11: Siemens versus P&F vs PROCENTEC DP/PA Link selection guide
Manufacturer/
Type
Siemens DP/PA Link
P&F DP/PA Link
(IM153-2)
(HD2-GTR-4PA)
PROCENTEC ComBricks
(Headstation, RS485 or FO DP module
and PA link modules)
DP/PA Link is a DP Slave.
Gateway
functionality
It is not transparent for the DP Master
(PLC). It is however transparent for
PA Device Manager/ Configuration
tools which are connected to the DP
network.
Independent of DP network.
PA Slave
addressing
PA Slaves behind the Link do not
“consume” DP node addresses.
First usable PA address is 3.
Number of PA
couplers behind a
DP/PA link
Transparent
(Note that the Link is nonetheless a DP
Slave and shall be configured with 1 Byte
I/O data)
Transparent
Part of the entire DP network (due to the
Links transparency).
Part of the entire DP network (due to
the Links transparency).
Each PA and DP device shall have a
unique node address across the whole
network.
Each PA and DP device shall have a
unique node address across the whole
network.
1-9
1-5
1-4
(Note: additional power module required
if more than 4 DP or PA modules are in
one ComBricks station)
Number of PA
Slaves per
Coupler
1-31
1-31
1-31
(Note: see 4.3 below for limits as per
this standard)
(Note: see 4.3 below for limits as per this
standard)
(Note: 4.3 below for limits as per this
standard)
Number of PA
Slaves per
Link/Coupler
arrangement
1-64
(Note: Shall not exceed 244 Bytes of
I/O per Link).
1-124
1-124
Number of PA
Slaves on one
Profibus DP
1-7936
1-123
1-124
(theoretically, 64 PA Slaves per
(123 PA Slaves across 4 couplers on one
(124 PA Slaves across up to 9 couplers on
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network.
Amount of data
DP/PA Link, 124 links in total)
244 bytes of I/O for all PA Slaves
behind each DP/PA link
DP/PA Link, note that the Link occupies a
node address too).
one DP/PA Link).
244 bytes of I/O per PA device.
244 bytes of I/O per PA device.
Standard
Bus parameters
Others
Watchdog time of PA network shall be
adjusted
Standard
Easy to configure if DP Master is a
Siemens PLC, more complex to
configure if DP Master is a nonSiemens PLC.
GSD files of each PA device shall be
converted. P&F does provide a conversion
tool for this.
Optional advanced PA network Diagnostic
module available.
(Note: Caters for individual adjustment
though if desired via the Headstations
web interface)
GSD files of each PA device is
recommended
to
be
converted.
PROCENTEC does provide a conversion
tool for this.
Allows direct fibre optic DP to PA
transition.
Out of the box DP and PA diagnostics
and 24/7 Network monitoring. (Ethernet
connection to ComBricks Headstation
required)
NOTE: The above table lists the maximum capabilities for comparison purposes which are not necessarily the permissible values as per this standard.
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Siemens DP/PA Link/Couplers Framework
(IM153-2)
DP
Master
DP/PA link “consumes”
1 DP Slave address.
PA Slaves do NOT
“consume” a node
address on the DP
network (Link is NOT
transparent).
Max. 244 Bytes of I/O
for all PA Slaves
behind the Link!
Pepperl & Fuchs DP/PA Link/Couplers Framework
(HD2-GTR-4PA)
Up to 7936 PA Slaves
per DP network
L
I
n
k
C C C C C
1 2 3 4 5
1-31 PA Slaves
per Segment
1-64 PA Slaves
per Link.
PA cycle time
per Link.
1-5
couplers
per Link
Up to 123 PA Slaves
per DP network
DP
Master
L
I
n
k
DP/PA link “consumes”
1 DP Slave address.
EACH PA slave
“consumes” a node
address on the DP
network (Link is
transparent).
C C C C
1 2 3 4
1-31 PA Slaves
per Segment.
Each PA Slave
with up to 244
Bytes I/O.
PA Cycle time per
Segment.
1-123 PA Slaves
per Link
1-4
couplers
per Link
PROCENTEC ComBricks DP/PA Link Framework
(Headstation, RS485 or FO DP module and PA link modules)
Diagnostic
PC
DP
Master
EACH PA slave
“consumes” a node
address on the DP
network (Link is
transparent).
Up to 124 PA Slaves
per DP network
HS DP
C C
C
...
1 2
9
1-9
couplers
per Link
1-31 PA Slaves
per Segment.
Each PA Slave
with up to 244
Bytes I/O.
PA Cycle time per
Segment.
1-124 PA Slaves
per Link
Figure 31: Siemens versus P&F vs PROCENTEC DP/PA Link Framework overview
Note that Siemens, P&F and PROCENTEC continue to develop their products which may lead to enhanced and/or slightly changed functionalities. It is the
designer’s responsibility to be aware of current DP/PA Link and coupler functionality and selection decisions should be based on current information (refer to
the product manuals).
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4.3
Number of PA Devices per Segment/Coupler
While it is in principle permissible to connect up 31 PA Slaves to a PA Segment (Coupler) this is to be
avoided for a number of reasons such as PA cycle time considerations, spurline length limitation, etc.
There shall be a maximum of 18 PA Slaves per PA Segment/Coupler.
Note that this number may be further limited by the current consumption, voltage drop and/or required
spurline length (see sections 4.4 & 4.5 below for more on this).
If a Siemens DP/PA Link is used, the maximum permissible amount of 244 Bytes of I/O data per
DP/PA Link shall also be considered, as this limits the number of PA Slaves DP/PA per Link. For
example, if a design has one Siemens DP/PA link with 3 PA Couplers and 18 PA instruments per
Coupler, even if each instrument is configured to only transmit one Analogue value (i.e. uses 5 Inputs
Bytes), the total amount of Input Bytes would be 270 Bytes for the DP/PA Link (3 Couplers * 18
Instruments * 5 Bytes Input).
Each coupler behind the DP/PA link creates its own PA Segment, if more than 18 PA Slaves are
required, it can be achieved by adding another coupler to the existing link or another DP/PA
Link/Coupler assembly to the DP network.
Preference should be given to keep the spurline of each connected PA device below 30 meters. This
way another 6 PA devices can be added to the PA segment at a later stage and each can still branch off
30 meters from the main PA trunk (see also section 4.4 below for more on this).
4.4
Spurlines, Splices and Cable length
The maximum permissible length of a (or each) spurline in a PA segment depends on the total number
of spurlines in the segment (note that this is not necessarily the total number of PA devices).
Total Number of Spurlines
1-12
1 -14
15-18
19-24
25-32
120m
90m
60m
30m
<1m
30m
30m
30m
30m
<1m
Maximum Length of
EACH Spurline (Not Ex)
Maximum Length of
EACH Spurline (Ex)
Table 12: Permissible Spurline length versus total Number of Spurlines per PA segment
“Spurs” with less than 1 meter cable lengths are considered “Splices” and are NOT counted as a
spurline. This is an important distinction as using splices may positively affect the maximum available
spurline length.
Consider the following example based on a PA segment with a total of 15 PA instruments connected
to it:
- The maximum spurline length would be 60 meters if each PA instrument is connected to the PA
trunk with a spurline of more than 1 meter in length.
- If it is possible to connect one (or more) PA instruments via a “Splice” to the PA trunk (cable
length less than 1 meter), each of the remaining 14 instruments can now be connected with a
spurline length of up to 90 meters (there are only 14 spurlines in the system now).
The maximum length of all Splices needs to be checked though and shall comply with the following:
Total PA Segment cable length (including spurs)
> 400 meters
Maximum TOTAL length of all splices per PA
Segment
8 meters
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< 400 meters
2% of total PA cable length
Table 13: Permissible Total Splice length versus total PA Segment cable length
The maximum segment length is 1900 meters per PA Segment. Note that the sum of all spurlines
shall be included in this value and that it is applicable for usage of Profibus PA cable type A. Note
further that this number also depends on the current consumption and voltage drop and spurline length
(see sections 4.4 & 4.5 below for more on this).
PA
Slave
4m
PA
Slave
To be avoided
11m Spurline
15m
Spurline
DP/PA
Link/
Couplers
“T”
Tap 0.5
m
The PA “Trunk” is the cable
between both termination points
T
Junction
Box
5m
Splice
Spurlines
“T”
Tap
“T”
Tap
0.5
m
“T”
Tap
rline
Spu
15
m
10
m
e
rlin
20m
PA
Slave
To be avoided
Spu
PA
Slave
Junction
Box
5m
T
15m
PA
Slave
PA
Slave
7m
DP
Master
PA
Slave
Figure 32: PA Segment Spurline, Splice and connection examples
With reference to Figure 31 the following applies to achieve simple, clean and easily maintainable PA
architectures:
- Only ONE PA Slave shall be connected to a Spurline (even though the PA standard permits
up to three PA Slaves per Spurline it shall be avoided to keep the design “clean”).
- Junction boxes shall NOT be connected to the main trunk via a Spurline (even though this
is generally permissible it shall be avoided to keep the design “clean”).
- Preference should be given to the use of Junction boxes with built-in Spurline protection. These
monitor the spurline current and protect the bus if a short circuit occurs on a spurline.
4.5
Segment Current consumption and Voltage Drop calculations
Owing to the bus powered nature of each PA segment, its design requires calculation of its current
consumption and Voltage drop to ensure proper operation.
The formula for the current consumption on a PA segment is:
Equation 2: PA Segment current consumption equation
I PASeg = (I D1BC + I D1FDE ) + (I D 2 BC + I D 2 FDE ) + ... + (I DnBC + I DnFDE )
 IPAseg < Is
IPAseg:
Total current consumption of the Segment
IDxBC:
Basic Current consumption of the Device
IDxFDE:
Fault Disconnection Electronics Current consumption of the Device
Is :
Current Supply of the PA Coupler
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PA devices limit their current in case of a failure to avoid short circuiting of the (powered) bus. The
fault current is known as the FDE value of the PA device (Fault Disconnection Electronics). The FDE
is the maximum current that the PA device may draw on top of its basic current consumption. The
FDE value is stated in the manual of the PA device (note that some PA devices do not have an FDE).
Since it is unlikely that all devices fault at the same time the following rules apply for the usage of the
FDE in the current calculation:
Number of FDEs to be included in current consumption calculation.
Number of PA devices per Segment
Always use highest FDES for worst case scenario
1-5
1
6-10
2
11-15
3
16-20
4
21-25
5
25-31
6
Table 14: FDE inclusion rules based on number of PA devices per Segment
Once the maximum current consumption per PA Segment is known a check is to be made to ensure it
does NOT exceed the power supply capability of the chosen PA coupler.
Following this, the voltage on the last PA device is to be calculated and checked (The “last” PA device
on the Segment is the one with the longest overall cable length to/from the PA coupler).
The formula for the Voltage drop calculation is:
Equation 3: PA Voltage drop equation:
U LD = U S − (I PASeg ∗ Rcable ∗ LSeg )
 ULD > Umin
ULD:
US:
IPAseg:
Rcable:
LSeg:
Umin:
Bus Voltage on last PA device
Bus Supply Voltage of the PA Coupler
Total current consumption of the Segment
Cable resistance per unit length (44 Ω/km for PA cable type A)
Length of ALL cables (including spurlines) in the Segment (in km)
Minimum specified operating voltage of the last PA device
Once the Voltage on the last PA device is calculated a check is to be made to ensure it is NOT
below its minimum specified operating voltage for the PA device.
Note: Pepperl & Fuchs Segment checker or ABB’s DTD 100 Profibus Layout tool may also be used
for this task; its results do not however relieve the designer from their duty of care.
4.6
Bus cycle time
Bus cycle times of PA networks are in general longer compared to DP. DP typical fast I/O updates
times are also not required on PA since its purpose is to contain analogue instruments and devices who
do not require signal update times in the low millisecond range.
The design shall nonetheless estimate the expected PA cycle time to ensure proper analogue control
and PID reaction times.
Due to the fact that Siemens and P&F DP/PA links operate differently in the way they buffer the PA
data and handle the underlying PA Segment couplers, they also have different ways to calculate the
PA cycle time. To make the PA cycle time calculation independent of the equipment selection, the
simplified formula below is to be used irrespective of the employed Links.
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The (simplified) formula to calculate the typical PA cycle time is:
Equation 4: PA cycle time equation
PAt = N PAS ∗ 15ms + N addCV ∗ 1.5ms + Acycl
Number of PA Slaves. 15ms is the typical data exchange time for a Standard PA
NPAS:
Slave with one cyclic value (i.e. 5 Bytes of data)
Number of every additional cyclic analogue value (5 bytes long) which
NaddCV:
increases the cycle time by an average of 1.5 ms.
Acycl:
Additional Acyclic component caused by the Device Manager Station (for
configuration, calibration, device data backup etc.). Assumed to be 20ms.
Siemens Link/coupler Note: The calculated PA bus cycle time is applicable for the whole PA network
behind the DP/PA link irrespective if the PA Slaves are located on one or across a number of couplers
behind the link.
P&F Link/coupler Note: The calculated PA bus cycle time is applicable and shall be calculated for
each individual PA segment behind the DP/PA link.
4.7
Termination
Each PA segment requires termination on either end of the segment. PA termination differs from DP
termination and comprises of a 100Ω (+/- 2 Ω) resistor in series with a 1μF (+/- 0.2 μF) capacitor.
Segment couplers (at the beginning of the PA trunk) have built in terminators. In some couplers the
terminator can be switched off, in other it is always terminated at the coupler. Some junction boxes
have a built in terminator that can be switched on or off when required. Unlike DP devices, the vast
majority of PA devices do not have inbuilt terminators.
The following PA termination rule applies (see also Figure 29):
- PA termination shall always be activated at the segment coupler which is considered the start of
the segment. The PA cable shall not be looped through the Segment coupler.
- The other termination shall be made via an external PA terminator which has to be located in
close proximity to the “last” junction box (the one farthest from the PA Coupler). Even though
non-EX rated PA junction boxes usually offer switchable inbuilt PA termination, this shall not
be used.
4.8
Device Manager PC
A PA Device Manager PC shall be included as part of the design.
This PC will be a permanent part of the installation and requires a connection to the Profibus DP
network (not the PA segments, the Device Manager software on the PC will access the PA instruments
via the DP/PA link).
Connection of the PC to the DP network is possible in two different ways:
1. Indirectly via an Ethernet to Profibus DP Gateway.
Indirectly by means of routing through the PLC onto the Profibus network.
The connection to the DP network via method 1 or 2 also means that a node address is required for the
Gateway or PC on the DP network. This is to be a Master node address and shall be the next free
address within the Master address range as per Table 6.
Preference shall be given to method 1 which has the following advantages over method 2:
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- The PC can be located anywhere on the SCADA Ethernet network (i.e. no need to run/extend
the Profibus cable to where the PC is meant to be located).
- One Device Manager PC can be used for all devices even if more than Profibus network (or
PLCs with Profibus networks) exists in the Plant.
Method 3 is a Siemens specific method and requires S7-400 hardware (and Siemens PDM Device
Manager software). It shall only be considered for larger Plants which have been designated to be a
Siemens PCS7 application.
4.9
Certification
Only certified PA slaves shall be used in the design.
4.10
Cable specification
PA Cable type “A” shall be used for all Profibus PA cables, it has the following characteristics:
Parameter
Value
Cable design
Twisted pair, shielded
Nominal Conductor cross sectional area
0.8 mm2 (AWG 18)
Loop resistance (direct current)
44 Ω/km
Impedance (31.25kHz)
100 Ω (+/- 20%)
Attenuation (39 kHz)
3 db/km
Capacitive asymmetry
2 nF/km
Max. propagation delay change (7.9 to 39 kHz)
1.7 μsec/km
Shield coverage
90%
Table 15: PA cable Type A specification
4.11
Explosion Safety
Explosion safety for Profibus PA is based on the FISCO model (Fieldbus Intrinsically Safe Concept,
developed by the German Federal Physical Technical Institute in cooperation with manufactures).
The FISCO model considerably simplifies the design requirements, installation and operation of
Profibus PA in hazardous areas. The model is based on the specification that a network is intrinsically
safe and requires no individual intrinsic safety calculations when the relevant four bus components
(field devices, cables, segment couplers and bus terminators) fall within predefined limits with regard
to voltage, current, power, inductance and capacity.
Intrinsically safe design for usage of Profibus PA in hazardous areas shall be done by a person whose
relevant competencies have been formally assessed as stated in DS 28.
The FISCO model is based on the following prerequisites which are to be adhered too in the PA Ex
design:
1. To transmit power and data the bus system uses the physical configuration as defined by IEC
61158-2 (which is the case with Profibus PA for example).
2. Each bus station shall fulfil the following capacitive and inductive requirements:
-
C < 5 nF
-
L < 10µH
3. The basic current consumption of a bus station is at least 10mA.
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4. The Bus shall be terminated at both ends with a PA typical RC terminator combination that
complies with the following:
-
R = 90 … 100 Ω
-
C = 0 … 2.2 µF
5. Only one active source is permitted on a bus segment (i.e. the PA coupler/PA power module),
all other components work as passive current sinks.
6. The Power, Current and Voltage that each device is capable of handling shall be greater or equal
to the Power, Current and Voltage that is supplied to it. In other words, the following applies:
-
UIn
>
UOut of related piece of equipment (e.g. PA coupler, Segment protector)
-
IIn
>
IOut
of related piece of equipment (e.g. PA coupler, Segment protector)
-
PIn
>
POut
of related piece of equipment (e.g. PA coupler, Segment protector)
7. The maximum permissible PA bus length including all spurlines is 1000 meters.
8. The maximum permissible Spurline length is 30 meters.
9. Bus cable shall comply with the following specification:
-
R’ = 15 … 150 Ω/km
-
L’ = 0.4 … 1 mH/km
-
C’ = 80 … 200 nF/km
Note that PA Cable type “A” fulfils this criteria.
Only FISCO certified devices are to be used in intrinsically safe PA designs which also automatically
ensures adherence to the requirements of item 2, 3 and 4.
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5
Installation
This chapter assumes that the Plant design incorporates a proper earthing and equipotential bonding
regime.
The Installer shall comply with the DP, PA and Profinet installation guidelines as listed in section 1.6.
5.1
Shield connection
The Profibus or Profinet cable shield shall always be connected at both ends of each cable run. The
only exception to this rule may come from installation requirements in hazardous areas where, for
instance, a capacitive shield connection may be called for (the design of this is to be done by a person
whose relevant competencies have been formally assessed.)
The cable shield shall be connected to a functional earth where the cable enters (or exits) a cabinet as
shown in Figure 33 below. Note that these shall not be used as a substitute for strain relief. Care
shall be taken when cutting off the outer sheath of the cable to avoid damage to the shield braid.
Figure 33: Cabinet entry/exit points cable shield connection examples
(courtesy Siemens Simatic Profibus
Networks Manual)
Pigtails shall not be used to connect the shield to the functional earth. Pigtails create an inductance
which effectively renders the shield to earth connection useless against high frequency interference.
Instruments or devices without provision for a shield clamp (i.e. terminal connection only) should be
avoided.
In-line DIN rail mounted Surge arrestors shall be equipped with a shield clamp as shown in
Figure 34 below.
Figure 34: Shield clamp usage for DIN rail mounted surge arrestors (courtesy Siemens Simatic Profibus Networks
Manual)
5.2
Cable handling and protection
Care shall be taken to prevent damage due to excessive tension or pressure, kinking or twisting as well
as bending radius violations.
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Manufactures specify a maximum tensile strength for the cable which shall not be exceeded during the
cable installation (e.g. pull by hand only without applying force).
Maximum bending radii as per the cable manufactures’ specifications shall be observed (if these are
not available the radius shall be greater than 10 times the cable diameter for permanent installations).
This is particularly important during installation within cabinets where excess cable is being “stored”
within the duct.
Cables shall not be run or laid over sharp edges. Cable glands are to be used for entry and exit to
cabinets.
Sections of cable which have been exposed to undue stress (e.g. been accidentally squashed, pinched,
kinked, twisted, stepped on etc.) shall not be used for the installation.
5.3
Cable spacing
Cables are classified into the following 4 categories according to their voltage level and application:
Category I: Bus signals, shielded (e.g. Profibus, Profinet, Ethernet)
Bus signals, unshielded (e.g. AS-Interface)
Data signal, shielded (e.g. Printer, counter inputs etc.)
Analog signals, shielded (< 25V)
Digital Process signals, unshielded (< 25V)
DC Voltage, unshielded (< 60V)
AC Voltage, unshielded (< 25V)
Category II: DC Voltage, unshielded (>60V and < 400V)
AC Voltage, unshielded (>25V and < 400V)
Category III:
DC and AC Voltage, unshielded (> 400V)
Telephone cable
Category IV:
Category I to III cables with direct danger of lightning strike
Cables from within each category can be laid together in common bundles or cable channels.
Figure 35 below shows the required clearance of Profibus or Profinet cables to cables from the other
categories if placed side by side. Cables of different categories may only cross each other at a 90
degree angle.
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Cable
Category
I
10cm
Cable
Category
II
20cm
10cm
50cm
Cable
Category
III
50cm
Cable
Category
IV
50cm
Figure 35: Air gaps Cable spacing requirements (side by side cable placement)
If it is not possible to maintain these distances, the Profibus or Profinet cable shall be run in steel
conduits or segregated from the other category cables by means of metallic partitioning of the cable
tray. Metallic partitions shall be electrically bonded to the cable tray.
5.4
Fast connect system
Only Fast Connect Cable and Fast Connect Plugs shall be used for the installation. Cable stripping is
to be done with the applicable Fast Connect Stripping tool. This avoids any potential for time
consuming and costly troubleshooting of the connection due to improper Stanley knife related cable
stripping.
5.5
Minimum Profibus DP cable length between devices
Irrespective of the chosen baud rate, a minimum of 1 meter cable shall be installed between two
neighbouring devices with an RS485 interface.
5.6
DB9 Connectors and Profibus installation cable path
DB9 connection for first and last
station on the bus
DB9 connection for all other
stations on the bus
Terminator
ON
Terminator
OFF
AB AB
11 22
Make sure that the Cable
Shield is in correct position
to ensure full proper
contact with shield clamp
in Plug!
AB AB
11 22
If termination is ON, the second
channel is disconnected.
Figure 36: DB9 Connector cable connection
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Figure 36, above, shows the correct connection method for DB9 connectors and what to watch out for.
Note that switching on the inbuilt termination resistor does not only “activate” the termination
resistors but more importantly disconnects the outgoing channel. Only DB9 plugs that offer this
feature are to be used (see recommend equipment list).
The disconnection functionality of the second channel is a very useful “feature”. It greatly helps in
cases of troubleshooting Profibus installations or if parts of the installation are required to be taken out
for maintenance work while maintaining the remaining bus with proper termination. For it to be
properly utilised though, the following cable path rule shall be adhered to:
Starting from the DP Master (PLC), the Profibus cable shall loop through each DB9 Plug by
“entering” it on the “left” and “leaving” it on the right as shown above (“left” and “right” as per
above).
Normal Situation
DP
Master
DP
Slave
DP
Slave
DP
Slave
DP
Slave
DP
Slave
DP
Slave
AT
Troubleshooting situation
DP
Master
DP
Slave
DP
Slave
DP
Slave
DP
Slave
DP
Slave
DP
Slave
AT
Activation of Plug
Terminator isolates
downstream path
Plug with Terminator ON
Plug with Terminator OFF
Figure 37: Designated Profibus Cable path example
Loop through connection on devices without DB9 connectors (e.g. terminal strip connection or M12
Plugs) still require adherence to the cable path rule.
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6
PLC and SCADA configuration
6.1
PLC configuration
Each PLC vendor uses their own configuration software to allow creation of Profibus or Profinet
related setup. While there may be differences in the user interface, the common aim is to facilitate the
setup of the bus parameters and configuration of all Devices irrespective of the manufacturer.
6.1.1
GSD files
6.1.1.1
Profibus
Configuration of each DP or PA Slave requires a corresponding GSD file for each Slave. A Profibus
DP or PA Device Manufactures may enhance or further develop the functionality of their products.
Since this may lead to revised GSD file being available it is imperative that the correct GSD file
version for the chosen Slave is being used for the DP Master configuration.
6.1.1.2
Profinet
GSDML files are used for the integration and configuration of Profinet I/O Devices. GSDML files are
simply GSD files written in XML (Extensible Markup Language). As with GSD files, it is imperative
that the correct GSDML file version for the chosen I/O Device is being used for the I/O
Controller configuration.
6.1.2
Device Watchdog time (Response monitoring)
Profibus Slaves and Profinet I/O devices incorporate a Watchdog functionality (sometimes also called
“response monitoring”). This is a time based monitoring mechanism inside the Device which monitors
the repeated (cyclic) occurrence of communication with the PLC. Devices will go into a safe state
upon expiry of their watchdog time. This is an important and useful feature to avoid potentially
dangerous Plant states in cases of communication problems or bus failures.
Depending on the Device and implemented functionality (consult the device manual), it may support
entering different pre-defined “Safe States” upon detection of a bus fault.
Safe state examples for a Valve actuator may entail:
-
Stay (e.g. actuator will remain in last position)
Open (e.g. actuator will open fully)
Close (e.g. actuator will close fully)
Move to position x (actuator will move to a configurable position value)
The following rules apply for Watchdog monitoring:
• Watchdog monitoring shall be enabled for each Device.
• The Safe state position needs to be defined for each Device and configured accordingly in the
DP Master or I/O Controller setup
The Safe state position needs to be defined for each Device and configured accordingly in the DP
Master or I/O Controller setup.
6.1.3
DP Master or I/O Controller bus monitoring
While the Devices themselves will go into a safe state if communication with the PLC is lost, the DP
Master or I/O Controller will also recognise “lost” devices. The associated PLC logic shall capture
Devices’ communication faults/dropouts (per individual Device) and raise a SCADA Alarm (per
individual Device) to inform the Operators that either device control has been lost and/or inputs are
no longer updated.
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Profinet and Profibus Network Design and Installation
6.2
Diagnostics
Apart from the “normal” cyclic I/O data exchange between each Slave and the PLC, Devices are also
capable of issuing Diagnostics data.
6.2.1
Profibus Diagnostics
The format of the first 6 Bytes of the diagnostic message are standardised cannot be changed by the
slave manufacturer. These 6 Bytes are the so called “Standard Diagnostics” and contain general
information related to the slave (e.g. the Device ID number, bits to indicate if it is parameterised, in
data exchange etc.).
Following these, the device/instrument manufacturer may choose to develop and add extended
diagnostic information which is specific for their device. The manufacturer decides on the meaning
and length of the extended diagnostic data for their Slave.
“Simple” slaves (usually non-modular ones like flow meters, pressure transmitters, valve actuators,
drives etc.) will typically have a predetermined fixed amount of extended diagnostic data. The
assignment of which bit has what meaning in the extended diagnostic messages can be found in the
slave manual and/or its GSD file (Note that not all manufactures chose to add these to the GSD file).
An example of some of the extended diagnostics bits from Profibus PA pressure transmitter are:
Unit_Diag_Bit(24) = "Hardware failure electronics"
Unit_Diag_Bit(27) = "Electronic temperature too high"
Unit_Diag_Bit(29) = "Measurement failure"
Unit_Diag_Bit(31) = "Device initialization failed"
Unit_Diag_Bit(32) = "Zero point error"
Unit_Diag_Bit(33) = "Power supply failed"
Unit_Diag_Bit(34) = "Configuration invalid"
Unit_Diag_Bit(66) = "A115: Sensor overpressure"
Unit_Diag_Bit(68) = "A120: Sensor underpressure"
Unit_Diag_Bit(72) = "A610: Calibration error"
An example of all of the extended diagnostics bits from a Profibus DP valve actuator are:
Unit_Diag_Bit(24) = "Motor Thermostat"
Unit_Diag_Bit(25) = "HI-HI Torque in Opening"
Unit_Diag_Bit(26) = "HI-HI Torque in Closing"
Unit_Diag_Bit(27) = "Actuator blocked in Opening"
Unit_Diag_Bit(28) = "Actuator blocked in Closing"
Unit_Diag_Bit(29) = "HI-HI Temperature"
Unit_Diag_Bit(30) = "Position Sensor Failure"
Unit_Diag_Bit(31) = "Speed Sensor Failure"
Unit_Diag_Bit(32) = "Main Voltage Fault"
Unit_Diag_Bit(33) = "K1 Contactor Failure"
Unit_Diag_Bit(34) = "K2 Contactor Failure"
Unit_Diag_Bit(35) = "Configuration Error"
Unit_Diag_Bit(36) = "Hardware Error"
Unit_Diag_Bit(37) = "Low Alkaline Battery"
Unit_Diag_Bit(38) = "Lost Phase"
Unit_Diag_Bit(39) = "No response from base card"
A slave will only inform the DP Master about the availability of diagnostic data if and when the need
arises. The DP Master will then automatically request these diagnostic data the next time it polls the
Slave.
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Diagnostic data of more “complex” slaves (e.g. modular I/O stations) on the other hand are generally
not fixed in their length and/or assignment of bits (owing to the freely configurable nature of the
Slave). While this makes PLC logic based evaluation of the received diagnostic data more “complex”
too, it is still desirable to do so.
As it can be seen from the above examples, diagnostic data yield important additional information
about the status of the slave, as such the following applies for the evaluation of them in the PLC logic
and SCADA system:
1. A general “Received Diagnostic message from slave xyz” is to be generated for every
slave (DP or PA, modular or not modular slave) and alarmed on the SCADA system.
2. A detailed diagnostic (popup) screen is to be configured for each slave with fixed
Diagnostic data assignment. This screen will display the details of the diagnostic
message. Consideration should be given to develop these for all Slaves including
“complex” ones.
Alternatively, a dedicated Diagnostic Station PC may be employed to allow read out and evaluation of
slave diagnostic data (Class 2 Master functionality). In cases where PA instruments are used, the PA
Device Manager Station PC shall be set up and used for this purpose.
6.2.2
Profinet Diagnostics
While even more comprehensive than Profibus Diagnostic data, the same intent and handling as
described in 6.2.1 above applies.
Figure 38: Siemens ET200MP GSDML file channel Diagnostic example
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Profinet and Profibus Network Design and Installation
Figure 39: Danfoss FC Series drive GSDML file channel Diagnostic example
6.3
Profibus DP Bus parameters
DP master configuration tools will generally opt for the default bus parameters as shown below for
500 and 1500 kbit/s.
500 kbit/s
1500 kbit/s
TSlot (bit times)
200
300
Max. TSDR (bit times)
100
150
Min. TSDR (bit times)
11
11
TSet (bit times)
1
1
TQuiet (bit times)
0
0
Gap factor
1
10
Retry Limit
1
1
HSA
126
126
Table 16: Default DP Bus parameters vs. Baud rate
The following three parameters of each DP network are to be modified in the configuration (this
improves network stability in general and allows “ride through” of short lived interference):
Retry limit: Change from 1 to 5
Min. Tsdr: Change from 11 to 22
TQuiet:
Change from 0 to 9
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7
Appendix
7.1
List of figures
Figure 1: Profinet Line Topology example
15
Figure 2: Profinet Line Topology example detail
15
Figure 3: Profinet Star Topology example
16
Figure 4: Profinet Tree Topology example 1 (multiple Star Topologies)
16
Figure 5: Profinet Tree Topology example 2 (Line and Star topology combined)
17
Figure 6: Profinet I/O Controller/Devices inbuilt switches based MRP Ring Topology example (information only, NOT to be
used in the design)
17
Figure 7: Profinet Switches based MRP Ring Topology example (MRP and Star combined)
18
Figure 8: Line Topology Network Load example (1ms update time, 24 Bytes Inputs and Outputs per I/O device)
22
Figure 9: Star Topology Network Load example (1ms update time, 24 Bytes Inputs and Outputs per I/O device)
22
Figure 10: Network load calculation tool usage example
23
Figure 11: Example SCADA and OIP connection
24
Figure 12: NOT allowed - multiple PLCs on one Profinet Network
25
Figure 13: Allowed - each PLC with its own Profinet Network
26
Figure 14: S7-400 H System "Open Ring" Profinet Network example
27
Figure 15: S7-400 H System with redundant Profinet Networks example
27
Figure 16 S7-400 H System with redundant Profinet Networks with “Y” switch
28
Figure 17: PN/PA Proxy usage example
29
Figure 18: PN/DP Proxy usage example
30
Figure 19 Example Fibre Optic Line Topology
33
Figure 20 Example Fibre Optic Ring Topology
33
Figure 21 Example Fibre Optic Star Topology
34
Figure 22: Example RS 485 Line Topology
35
Figure 23: Example RS 485 Tree Topology
35
Figure 24: Spurline example
Figure 25: Typical “loop through” connection
39
Figure 26: DP Repeater usage to avoid spurlines
40
Figure 27: DP Repeater Hub usage example
40
Figure 28: Profibus DP termination structure and DB9 connector pin assignment.
40
Figure 29: Correct and incorrect DP Segment termination examples
42
Figure 30: Typical PA Topology example including termination requirements & Device Manager Station
44
Figure 31: Siemens versus P&F vs PROCENTEC DP/PA Link Framework overview
47
Figure 32: PA Segment Spurline, Splice and connection examples
49
Figure 33: Cabinet entry/exit points cable shield connection examples (courtesy Siemens Simatic Profibus Networks Manual)
54
Figure 34: Shield clamp usage for DIN rail mounted surge arrestors (courtesy Siemens Simatic Profibus Networks Manual) 54
Figure 35: Air gaps Cable spacing requirements (side by side cable placement)
56
Figure 36: DB9 Connector cable connection
56
Figure 37: Designated Profibus Cable path example
57
Figure 38: Siemens ET200MP GSDML file channel Diagnostic example
60
Figure 39: Danfoss FC Series drive GSDML file channel Diagnostic example
61
7.2
List of Tables
Table 1: S7 CPU examples for I/O Device capability
19
Table 2: Profinet I/O devices 70% rule design limit 20
Table 3: Profinet update times selection table
21
Table 4: Network Load examples (24 Bytes of Inputs and 24 Bytes of Outputs per I/O Device) 22
Table 5: PN/DP Proxies differences
30
Table 6: DP Node address assignment Error! Bookmark not defined.
Table 7: Profibus DP Maximum Segment length versus Baud rate
38
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Table 8: Maximum permissible TOTAL Spurline length per Segment versus baud rate
Table 9: DP cable type A specification
39
Error! Bookmark not defined.
Table 10: Siemens versus P&F vs PROCENTEC DP/PA Link selection guide
45
Table 11: Permissible Spurline length versus total Number of Spurlines per PA segment Error! Bookmark not
defined.
Table 12: Permissible Total Splice length versus total PA Segment cable length
defined.
Error!
Bookmark
not
Table 13: FDE inclusion rules based on number of PA devices per Segment Error! Bookmark not defined.
Table 14: PA cable Type A specification
Error! Bookmark not defined.
Table 15: Default DP Bus parameters vs. Baud rate Error! Bookmark not defined.
7.3
List of Equations
Equation 1: Typical DP cycle time equation (Mono-Master system)(1) 37
Equation 2: PA Segment current consumption equation
Equation 3: PA Voltage drop equation:
Equation 4: PA cycle time equation
49
50
51
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7.4
Explanatory notes for Topology drawing 1 (Profibus with Siemens PA Link/Coupler)
DP Devices overview table
Node
Type
Input Bytes
Output Bytes
Comments
10
Filter 1 I/O station
8
8
2*32 channel Digital input cards, 2*32 channel Digital output cards
11
Filter 1 DP/PA link
45
0
Number of Input and Output Bytes is the sum of underlying PA devices Input and Output Bytes.
12
Filter 1 Valve 1
8
4
Based on data sheet of selected Valve
13
Filter 1 Valve 2
8
4
Based on data sheet of selected Valve
14
Filter 1 Valve 3
8
4
Based on data sheet of selected Valve
20
Filter 2 I/O station
8
8
See Filter 1
21
Filter 2 DP/PA link
45
0
See Filter 1
22
Filter 2 Valve 1
8
4
See Filter 1
23
Filter 2 Valve 2
8
4
See Filter 1
24
Filter 2 Valve 3
8
4
See Filter 1
30
Filter 3 I/O station
8
8
See Filter 1
31
Filter 3 DP/PA link
45
0
See Filter 1
32
Filter 3 Valve 1
8
4
See Filter 1
33
Filter 3 Valve 2
8
4
See Filter 1
34
Filter 3 Valve 3
8
4
See Filter 1
40
Filter 4 I/O station
8
8
See Filter 1
41
Filter 4 DP/PA link
45
0
See Filter 1
42
Filter 4 Valve 1
8
4
See Filter 1
43
Filter 4 Valve 2
8
4
See Filter 1
44
Filter 4 Valve 3
8
4
See Filter 1
101
VSD 1
28
28
PPO 5 type selected
102
VSD 2
28
28
PPO 5 type selected
103
VSD 3
28
28
PPO 5 type selected
104
VSD 4
28
28
PPO 5 type selected
420
192
I/O Bytes Total
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PA Devices overview table (Shown for one Filter, Filter 1-4 PA segments are identical)
7.4.1
Node
Type
AI/AO values
Current consumption
FDE
Min. operating Voltage
Comments
3
Flow Transmitter
2
12 mA
10 mA
9V
Actual Flow and Totaliser value
4
Pressure Transmitter
1
11 mA
0 mA
9V
5
Level transmitter
1
11 mA
0 mA
9V
7
Pressure Transmitter
1
11 mA
0 mA
9V
8
Flow Transmitter
2
12 mA
10 mA
9V
Actual Flow and Totaliser value
9
Analytical Transmitter
2
11 mA
5 mA
9V
PH and temperature value
Estimated DP cycle time:
Summary for calculation: Number of DP Slaves:
Total of all Input and Output Bytes:
Estimated DP cycle time:
7.4.2
𝐷𝐷𝐷𝐷t =
Estimated PA cycle time:
380 + 300 ∗ NDPS + BitDP ∗ TIOB
Bsd
+ 0.000075𝑠𝑠
Summary for calculation: Number of PA Slaves:
Number of additional cyclic values:
Estimated PA cycle time
7.4.3
24
612
=
9.6 ms
=
114.5 ms (per Filter)
6
3
PAt = 6 ∗ 15ms + 3 ∗ 1.5ms + 20ms
PA current consumption:
Summary for calculation: Number of FDE currents to be used: 2 (6-10 PA devices)
PA couplers supply capacity:
1000 mA
PA current consumption: I PASeg = (12mA + 10mA) + (11mA) + (11mA) + (11mA) + (12mA + 10mA) + (11mA)
=
88.0 mA (per Filter)
Result: OK (1000 mA available, 88 mA required)
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7.4.4
PA Voltage drop calculation:
Summary for calculation: PA Cable length:
PA couplers supply voltage:
PA Voltage drop calculation:
106 m (trunk length + length of all spurlines)
31 V
U LD = 31V − (0.088 A ∗ 0.044 Ω/m ∗106m )
=
30.59 V (at the PA device furthest from the Coupler)
Result: OK (30.59 V available, 9 V required)
7.5
Explanatory notes for Topology drawing 2 (Profibus with P&F PA Link/Coupler)
DP Devices overview table (Note: PA Slaves are counted as DP Slaves due to the DP/PA links transparency)
Node
Type
Input Bytes
Output Bytes
Comments
10
11
12
13
14
15
16
17
19
20
21
30
31
32
33
34
35
36
37
39
40
41
50
51
52
53
54
55
56
Filter 1 I/O station
Filter 1 DP/PA link
Filter 1 Valve 1
Filter 1 Valve 2
Filter 1 Valve 3
Filter 1 FT (PA device)
Filter 1 LT (PA device)
Filter 1 PT (PA device)
Filter 1 PT (PA device)
Filter 1 FT (PA device)
Filter 1 AT (PA device)
Filter 2 I/O station
Filter 2 DP/PA link
Filter 2 Valve 1
Filter 2 Valve 2
Filter 2 Valve 3
Filter 2 FT (PA device)
Filter 2 LT (PA device)
Filter 2 PT (PA device)
Filter 2 PT (PA device)
Filter 2 FT (PA device)
Filter 2 AT (PA device)
Filter 3 I/O station
Filter 3 DP/PA link
Filter 3 Valve 1
Filter 3 Valve 2
Filter 3 Valve 3
Filter 3 FT (PA device)
Filter 3 LT (PA device)
8
1
8
8
8
10
5
5
5
10
10
8
1
8
8
8
10
5
5
5
10
10
8
1
8
8
8
10
5
8
1
4
4
4
0
0
0
0
0
0
8
1
4
4
4
0
0
0
0
0
0
8
1
4
4
4
0
0
2*32 channel Digital input cards, 2*32 channel Digital output cards
Link is transparent but does have a Node address and 1 byte of input & output data
Based on data sheet of selected Valve
Based on data sheet of selected Valve
Based on data sheet of selected Valve
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57
Filter 3 PT (PA device)
59
Filter 3 PT (PA device)
60
Filter 3 FT (PA device)
61
Filter 3 AT (PA device)
70
Filter 3 I/O station
71
Filter 3 DP/PA link
72
Filter 3 Valve 1
73
Filter 3 Valve 2
74
Filter 3 Valve 3
75
Filter 3 FT (PA device)
76
Filter 3 LT (PA device)
77
Filter 3 PT (PA device)
79
Filter 3 PT (PA device)
80
Filter 3 FT (PA device)
81
Filter 3 AT (PA device)
101
VSD 1
102
VSD 2
103
VSD 3
104
VSD 4
I/O Bytes Total
5
5
10
10
8
1
8
8
8
10
5
5
5
10
10
28
28
28
28
424
0
0
0
0
8
1
4
4
4
0
0
0
0
0
0
28
28
28
28
196
PPO 5 type selected
PPO 5 type selected
PPO 5 type selected
PPO 5 type selected
PA Devices overview table (Shown for one Filter, Filter 1-4 PA segments are identical, only Node addresses differ)
7.5.1
Node
Type
AI/AO values
Current consumption
FDE
Min. operating Voltage
Comments
3
Flow Transmitter
2
12 mA
10 mA
9V
Actual Flow and Totaliser value
4
5
7
8
9
Pressure Transmitter
Level transmitter
Pressure Transmitter
Flow Transmitter
Analytical Transmitter
1
1
1
2
2
11 mA
11 mA
11 mA
12 mA
11 mA
0 mA
0 mA
0 mA
10 mA
5 mA
9V
9V
9V
9V
9V
Actual Flow and Totaliser value
PH and temperature value
Estimated DP cycle time:
Summary for calculation: Number of DP Slaves:
Total of all Input and Output Bytes:
Estimated DP cycle time:
𝐷𝐷𝐷𝐷t =
380 + 300 ∗ NDPS + BitDP ∗ TIOB
Bsd
48
620
(PA Slaves are counted as DP Slaves due to links transparency)
+ 0.000075𝑠𝑠
Uncontrolled if Printed
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=
14.5ms
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7.5.2
Estimated PA cycle time:
Summary for calculation: Number of PA Slaves:
Number of additional cyclic values:
Estimated PA cycle time
7.5.3
6
3
PAt = 6 ∗ 15ms + 3 ∗ 1.5ms + 20ms
=
114.5 ms (per Filter)
PA current consumption:
Summary for calculation: Number of FDE currents to be used: 2 (6-10 PA devices)
PA couplers supply capacity:
500 mA
PA current consumption: I PASeg = (12mA + 10mA) + (11mA) + (11mA) + (11mA) + (12mA + 10mA) + (11mA)
=
88.0 mA (per Filter)
Result: OK (500 mA available, 88 mA required)
7.5.4
PA Voltage drop calculation:
Summary for calculation: PA Cable length:
PA couplers supply voltage:
PA Voltage drop calculation:
106 m (trunk length + length of all spurlines)
30.0 V
U LD = 30V − (0.088 A ∗ 0.044 Ω/m ∗106m )
=
29.59 V (at the PA device furthest from the Coupler)
Result: OK (29.59 V available, 9 V required)
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Profinet and Profibus Network Design and Installation
7.6
Explanatory notes for Topology drawing 3 (Profibus with pure DP network, no PA)
DP Devices overview table
Node
Type
10
Filter 1 I/O station
11
Filter 1 Valve 1
12
Filter 1 Valve 2
13
Filter 1 Valve 3
20
Filter 2 I/O station
21
Filter 2 Valve 1
22
Filter 2 Valve 2
23
Filter 2 Valve 3
30
Filter 3 I/O station
31
Filter 3 Valve 1
32
Filter 3 Valve 2
33
Filter 3 Valve 3
40
Filter 4 I/O station
41
Filter 4 Valve 1
42
Filter 4 Valve 2
43
Filter 4 Valve 3
101
VSD 1
102
VSD 2
103
VSD 3
104
VSD 4
I/O Bytes Total
7.6.1
Input Bytes
Output Bytes
Comments
24
8
8
8
24
8
8
8
24
8
8
8
24
8
8
8
28
28
28
28
304
8
4
4
4
8
4
4
4
8
4
4
4
8
4
4
4
28
28
28
28
192
2*32 channel Digital input cards, 2*32 channel Digital output cards, 1*8channel Analogue input card
Based on data sheet of selected Valve
Based on data sheet of selected Valve
Based on data sheet of selected Valve
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
PPO 5 type selected
PPO 5 type selected
PPO 5 type selected
PPO 5 type selected
Estimated DP cycle time:
Summary for calculation: Number of DP Slaves:
Total of all Input and Output Bytes:
Estimated DP cycle time:
7.7
𝐷𝐷𝐷𝐷t =
380 + 300 ∗ NDPS + BitDP ∗ TIOB
Bsd
20
496
+ 0.000075𝑠𝑠
=
7.9ms
Explanatory notes for Topology drawing 4 (pure Profinet)
I/O Devices overview table
IP Address
192.168.0.2
Type
Switch
Input Bytes
0
Output Bytes
0
Comments
No cyclic I/O’s, excluded from calculation
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192.168.0.3
192.168.0.4
192.168.0.5
192.168.0.6
192.168.0.10
192.168.0.11
192.168.0.12
192.168.0.13
192.168.0.20
192.168.0.21
192.168.0.22
192.168.0.23
192.168.0.30
192.168.0.31
192.168.0.32
192.168.0.33
192.168.0.40
192.168.0.41
192.168.0.42
192.168.0.43
192.168.0.101
192.168.0.102
192.168.0.103
192.168.0.104
I/O Bytes Total
Switch
Switch
Switch
Switch
Filter 1 I/O station
Filter 1 Valve 1
Filter 1 Valve 2
Filter 1 Valve 3
Filter 2 I/O station
Filter 2 Valve 1
Filter 2 Valve 2
Filter 2 Valve 3
Filter 3 I/O station
Filter 3 Valve 1
Filter 3 Valve 2
Filter 3 Valve 3
Filter 4 I/O station
Filter 4 Valve 1
Filter 4 Valve 2
Filter 4 Valve 3
VSD 1
VSD 2
VSD 3
VSD 4
0
0
0
0
24
8
8
8
24
8
8
8
24
8
8
8
24
8
8
8
28
28
28
28
304
0
0
0
0
8
4
4
4
8
4
4
4
8
4
4
4
8
4
4
4
28
28
28
28
192
No cyclic I/O’s, excluded from calculation
No cyclic I/O’s, excluded from calculation
No cyclic I/O’s, excluded from calculation
No cyclic I/O’s, excluded from calculation
2*32 channel Digital input cards, 2*32 channel Digital output cards, 1*8channel Analogue input card
Based on data sheet of selected Valve
Based on data sheet of selected Valve
Based on data sheet of selected Valve
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
PPO 5 type selected
PPO 5 type selected
PPO 5 type selected
PPO 5 type selected
Uncontrolled if Printed
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7.7.1
Estimated Network load:
Summary for calculation: Number of I/O devices: 20
Average Input Bytes per I/O device: 16 (Roundup 304/20)
Average Output Bytes per I/O device: 10 (Roundup 192/20)
Result:
0.88% Network load
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© Copyright Water Corporation 2018
Design Standard No. DS 43-04
Profinet and Profibus Network Design and Installation
7.8
Explanatory notes for Topology drawing 5 (Profinet with GSDML file based PA proxy)
I/O Devices overview table
IP Address
192.168.0.2
192.168.0.3
192.168.0.4
192.168.0.5
192.168.0.6
192.168.0.10
192.168.0.11
192.168.0.12
192.168.0.13
192.168.0.14
192.168.0.20
192.168.0.21
192.168.0.22
192.168.0.23
192.168.0.24
192.168.0.30
192.168.0.31
192.168.0.32
192.168.0.33
192.168.0.34
192.168.0.40
192.168.0.41
192.168.0.42
192.168.0.43
192.168.0.44
192.168.0.101
192.168.0.102
192.168.0.103
192.168.0.104
I/O Bytes Total
Type
Switch
Switch
Switch
Switch
Switch
Filter 1 I/O station
Filter 1 PN/PA proxy
Filter 1 Valve 1
Filter 1 Valve 2
Filter 1 Valve 3
Filter 2 I/O station
Filter 2 PN/PA proxy
Filter 2 Valve 1
Filter 2 Valve 2
Filter 2 Valve 3
Filter 3 I/O station
Filter 3 PN/PA proxy
Filter 3 Valve 1
Filter 3 Valve 2
Filter 3 Valve 3
Filter 4 I/O station
Filter 4 PN/PA proxy
Filter 4 Valve 1
Filter 4 Valve 2
Filter 4 Valve 3
VSD 1
VSD 2
VSD 3
VSD 4
Input Bytes
0
0
0
0
0
8
45
8
8
8
8
45
8
8
8
8
45
8
8
8
8
45
8
8
8
28
28
28
28
420
Output Bytes
0
0
0
0
0
8
0
4
4
4
8
0
4
4
4
8
0
4
4
4
8
0
4
4
4
28
28
28
28
192
Comments
No cyclic I/O’s, excluded from calculation
No cyclic I/O’s, excluded from calculation
No cyclic I/O’s, excluded from calculation
No cyclic I/O’s, excluded from calculation
No cyclic I/O’s, excluded from calculation
2*32 channel Digital input cards, 2*32 channel Digital output cards
Number of Input and Output Bytes is the sum of underlying PA devices Input and Output Bytes.
Based on data sheet of selected Valve
Based on data sheet of selected Valve
Based on data sheet of selected Valve
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
See Filter 1
PPO 5 type selected
PPO 5 type selected
PPO 5 type selected
PPO 5 type selected
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© Copyright Water Corporation 2018
Design Standard No. DS 43-04
Profinet and Profibus Network Design and Installation
7.8.1
Estimated Network load:
Summary for calculation: Number of I/O devices: 24
Average Input Bytes per I/O device: 18 (Roundup 420/24)
Average Output Bytes per I/O device: 8 (Roundup 192/24)
Result:
1.056% Network load
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© Copyright Water Corporation 2018
Design Standard No. DS 43-04
Profinet and Profibus Network Design and Installation
END OF DOCUMENT
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