profbus DP communication to siemens S7-300 PLC

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SMVector: PROFIBUS-DP Communications to Siemens S7-300 PLC

Overview

PROFIBUS-DP is an internationally accepted serial protocol designed for

commercial and industrial automation control systems and distributed I/O devices

Scope

This document is intended to provide a helpful getting started guide for configuring a

PROFIBUS-DP master to correctly communicate with a SMVector drive and is aimed

to accompany the “SMVector PROFIBUS-DP Interface Reference Guide”

It is assumed that the user has familiarised themselves with how to navigate through

the drive parameters using the drive keypad display

Methods for configuring master devices can differ greatly between manufacturers The

details supplied in this document are intended for the configuring a Siemens / VIPA S7

-300 type PLC

Previous experience of using Siemens Step 7 PLC configuration software would be a

distinct advantage

The PLC handles the data transfer automatically, therefore no PLC coding or ladder

logic is required to initiate data transfer between the PLC CPU & the PROFIBUS-DP

interface However an example ladder program is provided for reference

Requirements

Hardware:

• SMV with firmware V2.6.0 or later

• SMV PROFIBUS-DP interface with firmware V1.01 or later

• A PC to PLC interface, either via PROFIBUS-DP or using the PLC MPI port

• PLC PROFIBUS-DP interface, if not fitted as standard depending upon the CPU

type (a VIPA Speed7 318 PLC with an integrated PROFIBUS-DP port was used

for this document)

Software & Firmware:

• Siemens Simatic Step 7 Manager (V5.4 used for this document)

• GSD & icon files for SMVector

NOTE:

It is also assumed that the user has correctly configured and tuned the SMVector with the

motor it is connected to

Drive Configuration

All SMVector parameters and settings are accessed using the drive keypad

Set the following drive parameters:-

1 Set the relevant motor and application parameters as required such as Accel

times and current limit etc

2 P100 - Start Control Source:

Set to mode 3

Other modes exist (see the drive Operating Instructions for full details), however,

only mode 3 allows full drive control from a PROFIBUS network

3 P121, P122 or P123 - TB13A, B & C Digital inputs:

Set one of the inputs to mode 9

It is possible to communicate to the drive via the network, but the drive control

word will on function when the chosen input is active

4 P400 - Network Protocol:

Set to 6 for PROFIBUS

5 P410 - Node Address:

Set this to the require address

The default is 126, but the valid address range is 1 to 125

6 The SMVector PROFIBUS-DP module has support for up to 6 cyclic data

channels in both directions However the The default mapping for SMVector

PROFIBUS-DP is 2 Data IN words and 2 Data OUT words, the configuration of

which is shown in following table:-

7 P418 - Re-initialise

Set P418 to 1 to activate any changes made to the module settings

8 The SMVector is now ready for use on the PROFIBUS-DP network

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Link # Mapped Function

IN 1 Drive Status Word

IN 2 Actual Output Frequency

OUT 1 Drive Control Word

OUT 2 Frequency Setpoint

NOTE:

• The terms “IN data” and “OUT data” refer to the data as seen by the PLC

Therefore, ”OUT data” goes OUT of the PLC to the network, while “IN data” comes

IN from the network to the PLC

• OUT data words should only be mapped to drive Read/Write parameters

Creating the Simatic project

1 Ensure that the Siemens Simatic Step 7 Manager software is correctly

installed before proceeding Follow the instructions that are supplied with this

software for more information

2 Using the Siemens Step 7 Manager configuration software, you can use a

wizard or manually setup the project by selecting File from the toolbar followed

by either New… or “New Project” Wizard… from the drop down menu, to

create a new project

3 If using the wizard then please follow the instructions given Alternatively if you

choose to manually set up the project, a window titled New Project will open

Under the User projects tab enter a project name, and then click on OK

4 The project window will now open Select Insert from the SITMATIC Manger

toolbar followed by Station from the drop down menu, and select the appropriate

PLC type, e.g 2 SIMATIC 300 Station

Enter the project name here

5 The SIMATIC Manager will now display the project with 2 icons in the right

win-dow Either expand the project tree on the left hand side or double click on the

PLC name icon until the Hardware icon is visible

6 Double click on the Hardware icon to launch the Hardware Configuration Utility

Hardware Configuration

1 If the Hardware list / catalogue is not visible in the right side of the screen, then

select View from the SITMATIC Manger toolbar followed by Catalogue from the

drop down menu to open the Catalogue window section

2 Before proceeding check if the SMVector GSD file is installed, by expanding the

PROFIBUS DP icon in the hardware list, followed by Additional Fieldbus

De-vices, then Drives If the drive you require is not listed, then the GSD file(s) will

have to be imported (See Appendix A later in this document)

3 Expand the SIMATIC 300 icon, and then expand the RACK-300 folder Drag and

drop the Rail icon in to the large left hand window This will then produce a Rail

list as shown below

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PLC icon Hardware

Configuration icon

4 Expand the PS-300 folder then drag and drop the appropriate PLC power supply

icon in to the Rail List slot 1

5 Expand the CPU-300 folder, expand the appropriate CPU type folder then drag

and drop the appropriate CPU to the Rail List slot 2 As shown (The CPU 318-2

model was used as the basis of this application which has a built in

PROFIBUS-DP port)

6 The PROFIBUS Network Properties window will automatically open (see below)

Set the Master Address to the required value and then select New

7 In the Properties-New subnet PROFIBUS window enter the network and author

names, any other useful information can be entered into the comments box

Switch to the Network Settings tab Select the required Transmission Rate

and set the Profile to DP Select OK to finish

8 The Interface Properties window will return but this time displaying the subnet

data Select OK to finish and return back to the Hardware Configuration

window

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9 If all the data has been entered correctly, the Rail List should now display a list of

components for the PLC and a chequered bus line labelled with the network

name that was chosen, trailing from the right hand side

10 Expand the Profibus DP icon at the top of the Catalogue list Expand the

Additional Fieldbus Devices folder, then the Drives folder

11 Drag and drop the relevant drive folder on to the chequered Rail List tail

12 The Properties-PROFIBUS interface window will appear again Set the

Address value to the require node address Followed by OK to finish

13 In the Catalogue section, expand the relevant drive folder then drag and drop the

required data format to the small lower left window section (See Appendix B for

data format details)

14 Repeat steps 11 and 13 to add as many nodes on to the network as required

and save the configuration

15 Check to ensure that the PLC CPU key / switch is the STOP position

16 Download the Hardware profile to the PLC, by selecting PLC from the Hardware

Configuration toolbar followed by Download to Module… from the drop down

menu

17 When the Select Target Module window opens ensure that the CPU that is to

be programmed is highlighted then select OK to finish

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18 Once the PC establishes communications, the Select node address window will

open If there is only one target station for the project then it will automatically be

highlight, otherwise select the appropriate station and select OK

19 The download progress bar will be displayed for the duration of the download,

after which the display will revert back to the HW Config window as per Step 13

20 Check the status LEDs on the PLC before switching the PLC into RUN mode

When in RUN mode the RUN LED should be illuminated If the BUSF (bus fault)

LED is illuminated double check the PositionServo and other slave device

set-tings ensuring that they were re-initialised correctly and that their setset-tings match

that of the Hardware Configuration

21 Check Node Status

Once initialised and the network detected the module will enter the “Data

Ex-change” state, i.e P419 = 4

If a different status is reported refer to the PROFIBUS-DP Communications

Module manual for further details

Appendix A – Importing GSD Files PROFIBUS Configurator

What are GSD files?

PROFIBUS-DP master configuration software uses the GSD files to configure the

network profile and communications with the relevant devices

For reference many manufacturers offer language specific GSD files for their

PROFIBUS devices, in which case the term and file suffix “GSD” is used for their

primary language choice and additional files for alternative languages will be named

differently, so for example with many European manufacturers where English is not

the primary language it may be possible to obtain GSD and GSE files where the GSE

file will have been coded so that the user configuration software displays the data

within the GSE file in English etc

GSD files are available form Lenze-ACTech website

GSD Files Installation

1 This procedure only needs to be performed once or after GSD file changes

2 Launch the “Simatic Step 7” software

3 Launch the Hardware Configuration sub package from within the main Simatic

Manager

4 If an existing project opens, close it

5 Select Options from the menu followed by Install New GSD

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6 From within Installing new GSD window, click on the Browse button to navigate

to the folder that GSD file(s) are located in Select either an individual or all

available GSD files then click on the Install button

7 Acknowledge the caution that pops up, OK the message when installation

complete then click on Close

8 The HW Config screen will re-appear The GSD file(s) will now be available and

will be listed as shown:

Appendix B - PROFIBUS-DP Data Types

Operation of the PROFIBUS-DP network is controlled automatically by the system in

the PLC The transfer of data values over the network must be initiated form the PLC

program itself

There are two ways of transferring data between the PLC and the remote nodes, the

choice of which depends up on the nature of the application

Non-consistent Data transfer can be used if there is no need to ensure new

references are transferred to the bus together This format allows data values to be

transferred directly to and from the peripheral I/O registers and therefore is simpler to

implement when writing the PLC code

Consistent Data transfer ensures that all data bytes are written to the data bus at the

same time This can be useful as it prevents data skew This occurs when the data

high and data low words of a reference are not transferred to the bus at the same

instant

Consequently, special function calls within the PLC must be used to ensure

consistency of data is maintained In the case of the Siemens Simatic software these

are:

• SFC14 to perform a write

• SFC15 to perform a read

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Appendix C - Example Ladder Logic Program

Example Program

1 Configure a network with just the PLC and a single Drive connected to the

PROFIBUS-DP network

2 Configure the PLC as described and ensure that the PROFIBUS-DP node

address on the drive is set correctly and ensure that the default mappings are

selected within the drive

3 The example program given below will generate a triangle wave reference, and

transfer the data value over PROFBUS-DP to the Drive The transmitted value

will be seen in parameter VAR_IREF

Using Simatic Step 7 - LAD/STL/FBD Editor

1 Enter the following ladder logic program into OB35, other OBs are available &

have different timed cyclic interrupts, ref to the Step 7 manager software help for

details (OB35 has a default scan time 100ms)

2 Connect to the PLC CPU using the appropriate PC to PLC adapter

3 Compile and download the program shown, then go on-line and set the PLC key

into RUN mode

4 Once the program has been downloaded successfully into the PLC, select PLC

from the toolbar followed by Monitor/Modify variables from the drop menu This

will open a watch window called Var-Variable Table 1 Setup the variable table

to monitor, this will allow the PC to either monitor or modify the PLC registers

(the PLC mode selection key will have to be in the RUN-P position) See on the

following page

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5 To enable the variable table to monitor constantly, select the glasses

icon

6 Enter the required values in to the watch window

Set MW2 to “1”

Set MW4 to “250”

Set MW6 to ”-250”

The value of MW0 should now ramp to 250 (25.0Hz) and down to 0 then through

to –250 before repeating the cycle

7 Ensure the drive hardware RUN and Network Enable are active

MW20 is used to access the SMV Control Word, which is constructed as follows

(see the PROFIBUS Reference Guide for more details):-

Writing a value of 0x0061 to MW20 will set BITs 0, 5 and 6 of the control word

The drive should now enable and follow the reference value of MW0