Transmission rates Endress+Hauser's PROFIBUS DP devices support baudrates up to 12 Mbit/s (depends on version).
The baudrate is automatically adjusted to that used by the master and must not be set at the device.
Similarly, PROFIBUS PA devices do not have to be adjusted, since the transmission rate is fixed.
On the other hand, if FieldCare or Commuwin II is used as a Class 2 master, both the transmssion rate and other bus parameters must be aligned with those of the segment coupler. The same PROFIBUS DP baudrate must be also be set in the network configuration software:
• Pepperl+Fuchs segment coupler SK1: 93.75 kBit/s
• Pepperl+Fuchs segment coupler SK2: 45.45 kBit/s - 12 MBit/s
• Siemens DP/PA coupler: 45.45 kBit/s
• Siemens DP/PA link: 9.6 kBit/s - 12 MBit/s
The typical values for the other bus parameters are listed in Table 7-12. Please note that for the Pepperl+Fuchs SK2 coupler, additional parameters must be set, as described later in theis chapter.
Table 7-12: Bus parameters for FieldCare and Commuwin II
Segment coupler Siemens P+F "old" P+F "new"1)
Slot time 640 10000 4095
Max. station delay time 400 1000 1000
Min. station delay time 11 255 22
Setup time 95 255 150
GAP update factor 1 1 1
Max. retry limit 3 3 3
Target rotation time2) (TTR) TTR calculated by master + 20 000 bit times
1) Segment coupler has the label with 12-3-98 or newer 2) Value must be set in all masters.
7.4.1 Aligning FieldCare
The FieldCare transmission rate is set in the PROFIBUS CommDTM:
1. Add the CommDTM for PROFIBUS to the network.
2. Right click on the CommDTM to opens the context menu. Select Configuration.
3. After changing the baudtrate, update the bus parameters and click on Defaults.
4. If necessary optimise the parameters as the manufacturer's specifications.
7.4.2 Aligning Commuwin II
The Commuwin II transmission rate is set in the DPV1 DDE server.
1. Start the server DPV1 from the File Manager or Explorer by a double click on the DPV1 icon in the Commuwin II program group.
2. Open the item Parameter Settings in the Configure menu. The baudrate can now be adjusted.
3. After the baudrate has been entered, update the bus parameters by clicking on Default.
4. If necessary optimise the parameters as the manufacturer's specifications.
7.4.3 Commissioning the Pepperl+Fuchs SK2
PROFIBUS PA-slaves Since the SK2 segment coupler works transparently, PROFIBUS PA stations are treated by the PROFIBUS DP master as if they were PROFIBUS DP slaves. This also applies to commissioning and configuration. In order that a PROFIBUS PA slave be placed in operation and be configured by a configuration tool, the GSD file of the slave must be integrated into the configuration tool.
In view of the fact that the SK2 coupler supports several transmission rates on the PROFIBUS DP side, the normal PROFIBUS PA GSD file cannot be used. Instead, the PROFIBUS DP GSD file is required. If the device does not support PROFIBUS DP, the PROFIBUS PA GSD file must be converted with the conversion program supplied by Pepperl+Fuchs with the SK2. This applies both to the manufacturer-specific and profile GSDs.
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Note!• The naming conventions for GSD files are described in Chapter 3.4.1.
• If you uncertain what GSD you have, integrate it into your configuration tool and check the transmission rates supported:
– If the transmission rate 31.25 kBd is supported, it is a PA GSD.
– If the transmission rates of 9.6 kBd to 1.5 MBd or 12 MBd are supported, it is a DP GSD.
GSD Converter If no PROFIBUS DP GSD exists, the PA GSD must be converted. The software can be downloaded free-of-charge from www.pepperl-fuchs.com. The task of this conversion software is exclusively to enter the missing transfer rate and set specific bus parameters to values that allow for problem-free operation of the PROFIBUS DP.
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Note!• The PROFIBUS user organization has agreed that certified GSD files that have been modified by the Pepperl+Fuchs GSD converter software do not lose their certificate.
The conversion of the GSD file imposes the following restrictions if the function was previously supported by the original GSD file:
• FREEZE and SYNC functionality is deactivated. These functions are used in PROFIBUS DP for synchronizing sensors/actuators. Since the system is working with transfer rates of up to 12 MBd on the PROFIBUS DP side (host side) and with a transfer rate of 31.25 kBd on the PROFIBUS PA side (field side) it is not possibleto ensure that this synchronization will work with no problems.
• A maximum of 4 master Class 2 connections (C2 connections) are supported for each slave.
Some PROFIBUS functions are currently not supported. If the field device is supposed to support one or more of the following functions, a warning will inform the user that this is no longer the case after the conversion. This affects the following functions:
• Alarms based on PROFIBUS DP V1
• The following functions of the PROFIBUS DP V2 – - Data Exchange Broadcast (Publisher/Subscriber) – - Time synchronization
– - Isochronous mode, i. e. cycle-synchronous transfer
Using GSD Converter After the program is started (pfgsdcv.exe) the following dialogue appears:
Fig. 7-6: Dialogue box: Pepperl+Fuchs GSD Converter
To convert a GSD file, proceed as follows:
1. Switch to the directory in which the GSD files to be converted are located.
2. Select the GSD files to be converted: You can select one or more files (using Ctrl or Shift) for conversion.
– Files with + before the file name are the result of a former conversion and generate an error message if you attempt to convert them again.
– Files with a - are not the result ofa conversion and can be converted. You can open a file to view it and edit it by double clicking on it.
3. Determine the version number of the GSD file to be converted: the name of a PROFIBUS GSD file always consists of three parts:
– The manufacturer-specific part (1- 4 characters) – The device ID number (4 characters)
– The file extension
For converted PROFIBUS PA GSD files, the Profibus User Organization (PNO) has specified that the charaters "YP0" and a version number as the the manufacturer-specific part of the name. You can select the version number using a drop-down box (revision) and thus generate different versions of GSD files for a field device (with the same ID number).
4. Switch to the directory in which the converted GSD files will be stored.
5. Convert the GSD files by clicking on the Process GSD --> button.
You can start the conversion process with this button. Another window appears in which you are informed of the results of the conversion process.
7.4.4 Watch Dog Time T
WDPROFIBUS devices can activate a watchdog mechanism that checks whether the PROFIBUS master is still actives every data exchange cycle. The time is measured in the PROFIBUS slave. If the watchdog is activated and the time TWD (Watch Dog Time) since the last cyclic call expires, the device quits cyclic data exchange mode, goes into the original state (Wait_prm) and sets the outputs to the secure state.
The value of TWD and the activation of the watch dog are transferred in the configuration telegram sent on start up from the PROFIBUS Master to the PROFIBUS slave (transition to the data exchange). In general, dimensioning of the time TWD is user-specific (not device-specific and not in the GSD). The lower limit of the value is given by the cycle time.
As a rule, the configuration tool is used to enter the time TWD. There are configuration tools for which the watchdog time is set at 1x of PROFIBUS master and others for which the watchdog time is set individually for each PROFIBUS PA station. The value is the same in both cases.
For many tools, the time TWD is automatically calculated based on the cycle time of the master with a corresponding transmission rate. At higher transmission rates on the PROFIBUS DP side (for example 12 MBd) cycle times on the PROFIBUS PA side may be longer by a factor of 300. If parameters were set directly for a PROFIBUS PA device using a high transmission rate, TWD is usually less than the PA cycle and the device never exchanges data.
Segment coupler SK2 To ensure reliable operation of the PROFIBUS the following bus parameters should be used:
• Transfer rate 45.45 kBd... 12 MBd
• Watchdog time TWD = 5 s
• PROFIBUS DP standard bus parameter
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Note!If there are a large number of PROFIBUS PA stations per channel of the SK2 segment coupler, the watchdog time TWD should be verified. The limit for the above value is about 32 stations, but depends on the volume of data to be transferred.
Determining TWD The above watchdog time is based on experience. If it is too long (slaves are not switching into the secure state quickly enough) or too short (slaves are switching into the secure state without the master ever having failed) this must be taken into the calculation. Depending on the configuration tool, you can:
• set parameters for only one watchdog time TWD for the entire PROFIBUS system.
In this case, the greatest delay time must be used as the basis for determining TWD.
• set parameters for a watchdog time TWD for each individual slave.
The time TWD set must be greater than the longest delay time TV_max that will occur:
TV_max = TCycle_DP + TCycle_PA_cannel
where TCycle_PA_channel = Cycle time of the PROFIBUS PA channel TCycle_DP = Cycle time of the PROFIBUS DP side
Pepperl+Fuchs recommends three times the PROFIBUS PA cycle time be used for the SK2.
Calculating TWD The PA cycle time TCycle_PA_channel depends on 1) the number n of stations on a channel and 2) the effective data length LΣ (total bytes input and output data of all devices/no. of devices): Cycle time can be calculated in an approximate manner as
TCycle_PA_cannel = n * (0.256 ms * LΣ + 12 ms) + 40 ms
For more information on calculating cycle time, please refer to the P+F instruction manuals.
8 Device Parametrization
This chapter describes the operating concept of the PROFIBUS PA devices and is subdivided as follows:
• PROFIBUS PA block model
• Functional survey
• FieldCare asset management software
• Commuwin II operating and display program
There are two reasons for parametrizing a PROFIBUS PA or DP device:
• the adjustment of the operating parameters of the device to calibrate it for the application at hand. In this case the corresponding operating instructions should be used.
• the adjustment of the profile parameters of the device in order to e.g. scale or simulate the cyclic measured value output to the PLC.
Profile parameters are accessible only through the acyclic services of the PROFIBUS DP system.
Local operation The operating parameters of most Endress+Hauser devices can be set up using the local operating elements of the device, if they are so equipped. This facility is provided in order that they can be set up before installation, e.g. on a test bench. It is not advisable to change parameters locally during the operation of a system, since this may have unforseen consequences, e.g. on control loops. For this reason, local operating should be disabled when the system is commissioned. More details on this function and the calibration of Endress+Hauser devices are to be found in the corresponding manuals.
Remote operation Device parameters can also be adjusted by the acyclic services of the PROFIBUS DP system, with an appropriate configuration program. This might be embedded within the system or run on an independent workstation. Endress+Hauser offers two alternatives: the FieldCar asset management ent software and the Commuwin II operating and display program. The latter is to be found in many existing plants, but will be gradually replaced over the next year.
This chapter contains a short overviewof the parametrization of devices via both these programs.
Full descriptions must be taken from the appropriatte device manuals.