PROFINET - Overview2

PROFINET is a member of a family providing industrial communications over Ethernet.

PROFINET is:completely standard Ethernet (IEEE802.3).

High speed, operating at 100Mbit/s or faster over copper or fibre-optic cables,

makes use of existing IT standards. But, is “real-time” and deterministic,

PROFINET is very well thought out to incorporate all the requirements of automation and control systems.

PROFINET is totally compatible with PROFIBUS but is NOT PROFIBUS over Ethernet.

PROFINET – Flexible, Open and backward compatible3

PROFINET

PROFIBUS v PROFINET4

Feature PROFIBUS DP PROFINET

Network size 126 devices max. Effectively unlimited

Data Rate Up to 12M bit/s 100 Mbit/s

Update rate and prioritisation

All devices have same update rate and

priority

Different update rates and priorities

Controlling Station Class 1 Master IO Controller

IO Equipment Slave IO Device

Diagnostic / Configuration Tool

Class 2 Master IO Supervisor

Protocols DPV0, DPV1, DPV2PROFINET RT, ARP, DCP, SNMP, LLDP,

TCP/IP, HTTP, MRP

IT services Not possible Integrated in devices

Real-Time Yes Yes

PROFIBUS v PROFINET5

Feature PROFIBUS DP PROFINET

TopologyTypically linear bus but tree and ring possible

Linear, star, tree and ring

RedundancyPossible but

manufacturer specificSimple and

standardised

Engineering accessChanges possible but

needs network restartPossible without

disrupting operation

Standard Diagnostics Yes Yes

Alarms Only on DPV1 Yes, with priority

Addressing By switch or over bus Over network

Network DevicesRepeaters, Hubs,

OLM’sSwitches

Termination Switch-selectableBuilt into RJ45

connector

Cable2 core shielded

twisted pair4 core shielded

twisted pair

PROFINET – Real-time v TCP/P6

PROFINET – In operation7

PROFINET

HTTP SNMP Socket

IP

TCP / UDP

Sensor system

PROFINET

PLC

PCSNMP/OPC server

PROFINET

Field devices

PCInternet Explorer

Real-TimeRT IRT

Ethernet

PROFINET allows for different data rates for different applications within the same network.

PROFINET - Topology8

PROFINET wiring is quite different to PROFIBUS

PROFIBUS:

Uses multi-drop segments with many devices on one cable. Segments are separated by repeaters.

Two-core screened twisted pair cable.

Termination is in the hands of the user – many problems arise because of this.

PROFINET :

Multi-drop connection is not used; all cables connect just two devices together. Switches are used for branching to devices.

Four-core screened twisted pair cable.

Termination is provided within every Ethernet device; no longer in the hands of the user – should eliminate termination problems.

PROFINET – Physical Layer9

Ethernet defines the physical layer and data link layer.Modern Ethernet is defined by the IEEE802.3 standard.PROFINET uses 100Mbit/s switched full duplex communication over copper or fibre optic cable.

100 BASE-TX copper cabling

100BASE-FX fibre optic cabling

PROFINET – Physical Layer (Cable)10

4-core shielded twisted pair cable.Link Class D - Cat5 or Cat5e cable for use at up to 100MBit/s.Characteristic impedance 100Ω.Cable length up to 100m maximum

TD+ yellow

TD- orange

RD+ white

RD- blue

PROFINET – Physical Layer (Connectors)11

PROFINET connectors are available for:

• “Inside use”– Within control rooms or cabinets

– RJ45 pattern

– Generally at least IP20 rated.

• “Outside use”– Exposed to the environment (field mounted)

– RJ45 pattern or

– M12

– Generally IP 65 to 67 rated

PROFINET – IO Devices12

Ethernet

IO-Controller

Configuration

Control/monitoring

Alarms

Diagnosis Diagnosis

Status/Control

Parameters IO-Device

PROFINET Supervisor

E.g. PLC running application program.

E.g. PC or laptop running engineering tool application.

E.g. Field device with inputs/outputs

(Compare with PROFIBUS Class-1 master)

(Compare with PROFIBUS Class-2 master)

(Compare with PROFIBUS Slave device)

PROFINET – Commissioning Guideline13

• This is one of several free-to-download guidelines documents from PNO (PROFIBUS and PROFINET User Organisation).

• It provides guidance on how to verify the installation aspects of the network as well as how to commission the live system.

• These tests are additional to the application-specific, System Acceptance Testing that would usually be performed.

Failure to follow these guidelines puts you at risk of having your application tests pass without a detailed knowledge of the underlying performance of your network !

PROFINET – Installation Acceptance14

These are associated with the cabling of the installation and include:

• Visual Checking of the cabling.

• Point-to-Point electrical testing of the cabling using a simple line tester.

• Point-to-point acceptance testing of the cabling using an Ethernet Function tester.

Installation Acceptance tests should ideally be performed by individuals who have Certified PROFINET Installer accreditation.

This is a one day course accredited by PI and delivered by organisations that have PI-certified Training Centre accreditation.

There are two such organisations in the UK.

PROFINET – Installation Acceptance – Visual Checks15

• The guideline lists 23 individual checks that should be performed on each cable. Examples are

• Cable laid according to plan?

• Maximum length of 100m observed?

• Cable screen earthed at both ends to a previously proven earthing system.

• Cable separation rules followed?

PROFINET – Installation Acceptance – Line Checks16

The main criteria for the simple electrical testing of PROFINET cables are:

• There are no short-circuits between any wires.

• There are no short-circuits between any wire and the screen

• There are no wire breaks.

• The shield is connected at both ends.

• The wire pairing has been observed correctly.

PROFINET – Installation Acceptance – Function Testing17

• Simple line testers are designed to test the electrical aspects of the cable.

• The more advanced function and acceptance testers establish the ability of that cable to successfully transmit predefined data packages as well as determine cable length, attenuation and cross-talk.

• Such tests are very useful as a baseline in the event of needing to perform such tests at a later date.

PROFINET – Commissioning18

These are associated with the operational aspects of the installation and should only be performed on completion of the Installation Acceptance tests.

• Checking that the addressing and naming of all IO devices are in conformance with the design specification.

• Determining other device-related information such as MAC addresses, Firmware versions etc.

• Establishing that the topology is in conformance with the design specification.

• Establishing the absence of discarded and error telegrams.

• Establishing operational characteristics – IO Device Cycle time, Net load, Jitter, Broadcast.

Installation Acceptance tests should ideally be performed by individuals who have Certified PROFINET Engineer accreditation.

This is a three day course accredited by PI and delivered by organisations that have PI-certified Training Centre accreditation.

PROFINET – IO Device Identification19

• Every PROFINET device has a world-wide unique MAC address assigned by the manufacturer.

• The MAC address is unique to that particular device and will change if the device is replaced with a spare.

• Before a device can take part in communications with an IO Controller, it must have been configured with a PROFINET Device Name. This is usually done with the configuration software of the IO Controller (e.g. Siemens TIA Portal) but can also be done using readily available PROFINET tools.

• When the IO Controller initialises communication with the IO Device, it will allocate an IP address to it.

• Every IO device will also have manufacturer-specific hardware and/or firmware versions.

• Note - All real-time communications takes place using MAC addresses.

MAC Address: 00: 0E:CF:04:68:7A

Device Name: MySensorName123

IP Address: 192.168.1.23

HW Version: 1.0

FW Version: 1.24

PROFINET – Topology20

Line

Tree

Star

Ring

PROFINET is very flexible when it comes to laying out the network.

However, each of the four shown come with advantages and disadvantages that need to be considered at the design phase.

It is important o ensure that the actual topology is in conformance with that described in the design specification.

PROFINET – Topology – Line Depth21

• Line depth is the number of forwarding switches between an IO Controller and an IO Device.

• The line depth will affect the cycle time that the device can be polled at.

• The choice of switch (store & forward / cut-through) also affects this (see next slide).

PROFINET – Topology – Switching technology22

STORE & FORWARD

CUT-THROUGH

PROFINET – Test for “Discarded Packets”23

• A switch may discard packets due to transmission problems or internal queue overflows at high network loads.

• This should be evaluated over a period of 60s at high network loads.

• During this period, there should be no discarded packets.

Missing Packets at high Load

PROFINET – Test for “Net load”24

• This is defined as the % of bandwidth used by the real-time communications.

• It should be checked at every IO Controller.

• The ideal value is <20%.

• Values in the range 20% to 50% - further investigation required.

• Values > 50% require actions to reduce the net load

Testing for Net Load

PROFINET – Test for “Broadcasts and Multicasts”25

• Occasionally, broadcast and multicast telegrams will appear on the network.

• These are telegrams that all devices on the network will respond to. Typical examples include:

• ARP broadcasts – Address Resolution Protocol telegrams are used during entire scans of the network and initiated by engineering systems, diagnostic tools and IT systems. Values > 0 and for entire IP ranges should be investigated.

• DCP multicasts – Device & Configuration Protocol telegrams are generated by an IO Controller on start-up to search for devices with a given device name prior to allocating an IP address. Values > 10 are considered high should be investigated, those > 20 are considered too high for trouble-free operation.

• MRP multicasts – Media Redundancy Protocol telegrams are used to determine data flow direction in ring topologies. Values > 0 should be investigated.

Note – these values can be checked at any point on the network, including a spare port on a switch.

PROFINET – Test for “Jitter”26

The organisation of PROFINET timing ensures that real-time communication with a particular device is achieved with a regular update time.However, it is possible that delays within switches and devices can cause the transmission time to vary from cycle to cycle.Such variable delays can give rise to “jitter”.Jitter is something that should be evaluated.

Update timeTime

Jitter Jitter

PROFINET – EMC Criteria27

• EMC (Electromagnetic Compatibility) and Protective Earth (PE) issues are acknowledged as being the cause of a significant number of problems on Fieldbuses and Industrial networks like PROFIBUS and PROFINET.

• This is because of the ever-increasing frequencies that such systems operate at.

• Simply ensuring that the cable screen is connected to earth at both ends serves no purpose if the earth loop impedance at “typical” frequencies is too high.

• The screen impedance of all PROFINET cables should < 0.6Ω and the current >0mA AND < 40mA.

• The impedance of the Functional Earth at “typical” frequencies should be <0.3 Ω.

• Any values outside of this range should be investigated.

PROFINET – Monitoring Tools - Operational Qualification28

TO PROFINET NETWORK

Internet Explorer

This permanent monitoring solution can be used during qualification and on-going support.

It has no effect on the PROFINET network which will continue to operate even if power to the monitor is removed.

24v

Volt-Free Contact to PLC

PROFINET – Acceptance Specification29

• This document acts as a formal record of the installation and operational qualification tests.

• It should clearly define roles and responsibilities.

• Define the type of tools required to perform the tests and typical specifications.

• Each test should cross-reference back to the appropriate section in the relevant design specification.

• Have clear descriptions of the tests and unambiguous acceptance criteria.

• There should be space available for the tester to sign/date each test and make notes.

Peter Thomas

(Control Specialists Ltd)

Chairman of the

PROFINET & PROFIBUS International Training Centres

(PITC‘s)

Peter Thomas

Control Specialists Ltd

PROFINET – Questions?

Profinet network qualification - Peter Thomas

Engineering

Transcript of Profinet network qualification - Peter Thomas