1. Tim Linnell (Eurotherm Ltd)
Profibus
Tim Linnell (Eurotherm Ltd)

2. This Talk Brief overview of Profibus family
Profibus DP - Where it came from, how it works
Profibus GSD Files
Profibus Slave Operation
Eurotherm GSD File editor
Future

3. Profibus Family Profibus DP Profibus PA Profibus FMS
Fast transfer of time critical I/O data
Machine building/Automation ~ 10mS scan time
‘DPV1’ adds ‘Acyclic’ messages and high level data type definitions
Profibus PA
DPV1 Messaging + Device Profiles + Intrinsic Safety
Slower Physical Medium (31.25 kbit/s) with loop power
Process Applications
Profibus FMS
‘Full’ Messaging (I/O + non time critical)
Higher level Communications (PLC <-> PLC)

4. ‘Traditional’ PLC Control System
Internal ‘Backplane’
Transfers Input and Output data
between CPU and Modules prior
to PLC scan cycle
Data from modules ‘appears’
in I/O registers in the CPU.
Processed by application
Point to Point wiring to Plant - Essentially 1 wire per signal

5. PLC Control With DP Internal backplane replaced by
external High Speed RS485 cable
connected to Scanner Module.
I/O data from devices is transferred
cyclically - ‘appears’ in PLC registers
to be processed by application.
Modules replaced by ‘Devices’ -
I/O or special function

6. Cyclic I/O Data Transfer
Slave Input Data (To PLC)
PLC Registers
Temperature
Working Setpoint
Loop Output Power
Alarm Status word
Slave Output Data (From PLC)
Target Setpoint
Manual Output
Application uses
data from input
registers and
sets values in
output registers
Scanner transfers I/O
Data from/to PLC once
each scan cycle for each
slave ~ 10mS cycle

7. General Benefits of using Fieldbuses
Wiring Cost reduction ( % of total)
Easier maintenance, and flexibility to add new devices when and where needed
Use ‘best of breed’, specialised, devices easily at all points in the application - reduces load on PLC
Devices located close to point of application and closely coupled to it
Feedback from smart devices reduces planned maintenance and allows quality improvement via SPC etc.
Not limited to modules produced by vendor of PLC (or PC3000!)

8. DP is popular with users...
Easily understandable - no need to read the spec!
Easily applicable - devices interwork without problems
Transparent to PLC programmers
Very little ongoing network maintenance
Supported by a very wide range of device and PLC vendors
DP systems are now being constructed on a very routine basis without problems - not an R&D exercise.

9. DP is popular with vendors
Based on a range of Siemens ASICs - easy hardware implementation for slave devices
Pre-Canned modules available (Siemens, Hilscher, SST etc) to add DP to products without significant hardware development
Easy to support - ASICs ensure third party devices work in a consistent and predictable manner
Result is a healthy proliferation of different kinds of I/O and specialised devices

10. Why Eurotherm chose Profibus DP
DP is currently the best choice for networking PLCs with I/O and other devices. Fast, simple, and available.
DeviceNet is too limited in bandwidth for larger applications, and third party support not as comprehensive.
Foundation Fieldbus not widely adopted.
Profibus DP now adopted within Eurotherm as our main Fieldbus platform.

11. Profibus - Weaknesses.
Limited ‘acyclic’ capacity. Not good for SCADA or large scale file transfers.
Not really plug and play (like DeviceNet)
No pre-defined Function Block library (like FF)

12. Eurotherm’s Profibus Range
SCADA - PC Cards
Wonderware, Wizcon, Interlution
T940
PC3000/PC300
T800
subselect.me OK
2900 e
CPU
Heat
Temp
Inner Temp
Main Air
Main Fan
Aux Air
Aux Fan
Run
Cool
Raise
Lower
Reset
Hold
Servo
Fridge
Light 1
Load
Light 2
Loop
Relay 4
DI/DO 8
2000F PID
Controllers
Thyristor
Power
Controllers
T630 Process
Controller
AC/DC
Drives
Chart
Recorders
2500
Multi-loop

13. GSD1 Files
Define third party devices to Profibus DP network configuration tools.
Include timing information, supported baud rates, links to bitmap images, etc.
Include details of I/O Mapping and ‘Parameterisation’
Contents downloaded to Slave devices on network startup
In Eurotherm products, define the set of device variables transferred over Profibus. Set up using our ‘GSD File Editor’
1Gerätestammdaten

14. DP Network Configuration
GSD
GSD
GSD

15. DP Slave Operation Units first ‘parameterised’ by Master
Sends up to 244 bytes of Vendor Specific Data
Data comes from GSD file
In Eurotherm devices, defines content of I/O messages
Units then ‘Configured’ by Master
Up to 244 bytes Type and Size data defining I/O
Slave enters ‘Data Exchange’
Exits back to parameterisation on timeout
“Diagnostic” requests made on status change or fatal error
“Diagnostics”
Not well understood (even by Siemens!)
Flagged during I/O exchange
Provide indication of Fatal Device Fault or
Provide indication of Status (e.g. sensor fail)

16. Profibus DP “Slave State Machine”
“Config Data”from GSD File
“User Parametisation Data ”from GSD File

17. Why Use a GSD Editor?
Profibus designed for simple bulk I/O devices (e.g. 16 words I + 0)
Our products are much more complex ( parameters).
Impossible to choose a universal subset for I/O, and wasteful of bandwidth to transfer unnecessary variables.
Best approach to allow I/O mapping selection by users on a per application basis

18. Problems
GSD file provides user data. Obvious place to define I/O transfer, and values from file may be changed by user using network configuration tool
However data type definitions are also in the GSD file, and closely coupled to I/O definition.
Data type definitions are not usually changeable using the network configuration tool
Solution Chosen - Create a GSD Editor tool to define I/O transfer in users’s terms, and manage type definitions automatically...

19. Eurotherm GSD File Editor
Creates Custom ‘GSD’ file for use by network configurators

20. Why Use the GSD File editor
Very easy to use - drag and drop interface
Allows optimum use of network ‘bandwidth’ - only transfer the variables you need
Permits very flexible use of devices - no need for a ‘lowest common denominator’ mapping
Avoids manual editing of GSD file employed by other vendors - error prone and complicated
Build up a library of GSD files for different applications
Use the PLC to ‘wire’ between device variables for complex control strategies
‘Web’ button for latest hints and tips on-line

21. Demand Data Cyclic Data interchange is great, but…
Relentlessly overwrites values set via the front panel of the instrument (though this can be overcome with sequence logic)
Allows access to a limited number of device variables
‘Demand Data’ provided to solve this problem
Uses 4 words in the input and output areas
Allows read or write access to all device variables ‘on demand’
Uses a simple ‘mailbox’ system, easily programmable using a PLC sequence program
Switched on or off by the GSD File Editor
Supported by specialised PC3000 Function Blocks
DPV1 provides “proper” acyclic messaging (currently 2500 E-Suite only)

22. Future Profibus group pushing ProfiNet (Profibus on Ethernet)
Various other developments (Plug and Play, ProfiSafe, Expansion of Profibus PA).
May be better long term bets for higher level Ethernet protocols (e.g. FF)

23. Conclusion
Profibus DP allows easy interconnection of Eurotherm and third party devices
Good for small scale “Machine Building” networks
Less good as a SCADA network
GSD file editor and ‘Demand Data’ allow great flexibility of operation with Eurotherm slaves.