Siemens SIMATIC Step 7 Programmer's Handbook

Siemens S7 Family

This handbook is a collection of programming overviews, notes, helps, cheat sheets and whatever that can help you (and me) program a Siemens PLC.

If you have experience with Siemens then please contribute.


Siemens Website Quick Links

This is a listing of tutorials and manuals found on the Siemens automation website that will get you started on the SIMATIC Step 7 software for S7-300 and S7-400 systems. From a new users perspective I’ve only heard disparaging comments about finding the right information on the Siemens’ website. I have to agree. Its information overload at it’s best. There’s a lot of different stuff there thrown together and found in different spots with very long URL addresses to add to the confusion.

Have no fear.  We’re here to help.  So we’ll look at the essentials for your journey. 

Of course the best type of training is the hands on type but if that’s not an option then you’ll need to start digging in.

Who’s got the Software?

If you are just learning and can’t easily get the software then there are two options.

  1. Order the demo CD which will give you a free 30-day trial period.  
  2. Download a free working copy of Step 7 Lite.  There are differences between the regular version of Step 7 and Step 7 Lite but for learning purposes you can go along way with the free Lite version.  

First Things First

The first thing I like to do with a new product is get an overview of everything.  Getting used to part numbers and product groupings can go a long way with your comfort level.  The best thing for this is the sales catalog (ST 70 – 2005).  You can also order a hard copy.

Where to Start?  Manuals, manuals, everywhere!

Once you install the Step 7 software there will be a directory under the SIMATIC folder called Documentation that includes the most important manuals.  Hard copies can be ordered with number 6ES7810-4CA08-8BW1.  Here’s how I would digest them.

  1. Working with STEP 7 - This is a basic introduction to Step 7 which walks through an example of controlling engines.  While it’s not the complete picture it does ease you very well into the learning curve of the Step 7 software.
  2. Programming with STEP 7 Manual - Here’s the fuller manual for the programming interface which is also the same as the online help accessed by pressed the F1 key.
  3. Configuring Hardware and Communication Connections STEP 7 Manual - Everything to do with the Hardware Configurator.
  4. Statement ListLadder Logic, and Function Block Diagram Reference Manuals - These manuals contain both the user’s guide and the reference description of the programming language or representation type. You only require one language type for programming an S7-300/S7-400, but you can mix the languages within a project, if required.  If you’re more comfortable with Ladder Logic or Function Block Diagram then start there but sooner or later you’ll have to become familiar with Statement List.
  5. System Software for S7-300 and S7-400 System and Standard Functions Reference Manual - The S7 CPUs have integrated system functions and organization blocks included with their operating system, which you can use when programming. This manual provides you with an overview of the system functions, organization blocks, and loadable standard functions available in S7, and detailed interface descriptions for their use in your programs.

Training Material

There’s gold in that website if you just do a little digging!  If you’re having a tough go with the manuals then you should definitely download the training material.  There’s a lot more screen shots and even a picture of a balding pudgy guy to point things out to you. What more could you want?

Flash Tutorials

If you’re not the manual type (and even if you are) check out the Siemens Step 7 Flash tutorials.  These are very professionally done with a nice sounding narrator to take you through all the basics of the Step 7 software and hardware.

What's Next?

Of all the starting places to dig for more info I find the support section the best especially if you have a part number or key word you can search on. Clicking on the Product Support link will bring up a tree on the left hand side that can be expanded down to the product of your affection.  Good luck and happy hunting.

Siemens Website



Review of Siemens SIMATIC Step 7 Lite Programming Software

“Great taste. Less filling.”

Siemens Lite Beer

When one hears the words “Lite” and software you tend to think of software that’s not really usable. Depending on your needs this may not be the case with the Siemens STEP 7 Lite package. The four major limitations in STEP 7 Lite verses the more advanced STEP 7 package are:

  1. Support limited to the SIMATIC S7-300 PLC, the C7 all-in-one PLC and HMI, and the intelligent CPUs of the ET200 distributed I/O family. So no programming for the S7-200 or S7-400 PLC series.
  2. No networking whatsoever. Remote I/O racks (IM modules) are supported but there’s nothing for Profibus DP even if you have a DP port on your CPU.
  3. No support for multi-projects or HMI integration.
  4. No communication processors (CP) or function modules (FM) supported.

If you’re interested in more details then refer to our chart of differences between the Step 7 program packages. So there are quite a few major limitations with the Step 7 Lite software which may end your further reading of this review.

On the other hand, the current availability of a free download of the SIMATIC Step 7 Lite software makes it awfully tempting to take a look at it. If your only use of Siemens PLCs are an S7-300, C7 or ET200 in a stand alone application with no special needs (CP or FM) then I could highly recommend the Lite package. It has the same level of programming functionality as the regular Step 7 packages plus some nifty interface enhancements to make it easier on the eyes and on the brain. It is possible (though not easy) to convert any software created in the STEP 7 Lite to STEP 7 and visa versa keeping in mind the limitations of the Lite version. Since the packages bear a lot of similarities it will also be easy for the student to transfer any learning on the Lite package over to STEP 7.

First Impressions

For a user of the regular STEP 7 software the first thing to notice is there is no SIMATIC Manager. That’s because the Lite version doesn’t support multi-projects or networking. The STEP 7 Lite software opens right up to the editor screen.

S7 Lite First Screen Shot


The overall aim of the Lite package was to make the interface easier for new users. I think they’ve done that while making it friendlier for everyone involved. The added graphics and color are a welcome addition. Another nice friendly feature is the extended hover help on the menus and icons where clicking on the tool tip expands it into more help text. On that note all the pop up dialogs are clearer then its STEP 7 counterpart.

One of the major differences can be seen on the left hand side window. Pretty much everything the programmer needs for maintaining the project is neatly organized here. There’s even a convenient thumb tack to pin it or make it automatically slide in and out when needed.

On the right hand side is the old familiar tree structure of commands and blocks. It’s missing the quick little reference help window on the bottom which has been replaced by just hovering your mouse over the command to get a fuller title (the F1 key works just the same too). The FC and FB blocks have been moved from here to a more logical place in the project window on the left hand side.

The Left Side Bar – CPU Overview and Project Window

S7 Lite Side Bar

The top portion introduces a CPU box with easy access to controls, diagnostics (Ctrl+D) and setup of the CPU. That’s not something I feel is necessary to be there all the time so I minimized it. Too bad there’s no apparent way to just get rid of it all together.

The Project Window below it is great. Everything’s is here from hardware to documentation. Something that just thrilled me is the tabs below that separate the offline and online versions of the program. On the regular STEP 7 software there is often a confusion between when you are offline or online. STEP 7 Lite minimizes that confusion by also provided clearly differentiated color schemes for when you have a block open online. And if that wasn’t all, the symbols beside the hardware and each block instantly tell you of differences between the offline and online versions of your program. You can just hover the mouse over the symbol to get more detail.

It’s also nice to have all the blocks clearly color coded and nicely arranged. You can drag and drop then anywhere in the list. There’s even a new feature of “Category” which is simply an organizational label inserted between blocks. In this screen I’ve inserted the category “Engine Data” and “Special Data”. This could be really helpful for logically grouping blocks in larger projects.

I also like the new way of creating blocks. From the pull down menu select Insert | Block … and this nifty dialog box pops up with all the selections on it. Even the OB selection has a nice drop down box of all the OBs available with its symbolic name.

The Hardware Manager

The greatest change of all is the overhauled hardware manager. The layout is great and is to be expected without the need to factor in networking. Just drag and drop your hardware on the picture and away you go. There’s even a nice hardware comparison feature clearly showing any differences between the offline and online setups.

S7 Lite Hardware Manager

The Editor

Much of the editor is like its big sister STEP 7. One noticeable part that’s “missing in action” is the detail view that gives quick access to info, cross reference, address info, etc. One part I like is a slight revamp of the declaration table. Instead of the tree like structure it’s one simple table with a column indicating its declaration. That means no having to dig through the tree just to see all the declaration variables.

S7 Lite Editor


Other then what we’ve all ready listed there are no other major differences. The symbol table, monitor/modify (a.k.a. VAT), and the reference data are all very similar to STEP 7. Overall, if you can live with the limitations, the STEP 7 Lite version is a great little package. Hopefully some of the better implementations will find there way into the STEP 7 software.

P.S. One little caveat is that it kept crashing on my plenty beefy enough Windows XP Home computer. Save often, arrgh!

Step 7 Connecting, Downloading and Uploading

These are general guidelines for connecting, downloading and uploading from an S7-300 or S7-400 PLC. The following procedures were created using Siemens SIMATIC STEP 7 version 5.4 software.

To start, open the SIMATIC Manager.

Now follow the links below.

Connecting to the S7 PLC

The Programming Cables

There are three major types of programming cables:

1. The CP5512 card in a PCMCIA slot.

2. The PC Adapter using a serial or USB connection

3. An Ethernet cable

The CP5512 card and the PC Adapter can communicate on either an MPI or PROFIBUS port. Note that PROFIBUS is labeled as DP on the Siemens connection ports. These cables can piggyback on existing connectors. Be aware that the PC Adapter draws its power to work from the connection port so check the power LED for proper operation. The CP5512 card draws its power from the computer.

For Ethernet (TCP/IP) use a standard Ethernet cable from the computer to a CPU with an Ethernet port, a CP 343/443 module or a network switch all ready attached to the PLC network.

Checking Communications

With the programming cable plugged in, you can check for proper operation by clicking on the Accessible Nodes icon.

If communications are successful, you'll see a window pop up similar to the one below. If so, then close the Accessible Nodes window and proceed to the download or upload section.

If communication fails then you will receive a message like below.

This indicates that the cable is not in the right computer port or the cable is not plugged in properly.

Setting the PG/PC Interface

In order to start communication to the PLC you will need to match the "PG Interface" setting with the programming cable and protocol. To do this, select the menu Options > Set PG/PC Interface.

The following dialog box will open up displaying all the different interfaces (i.e. communication drivers).

Each cable has its own interface. For Ethernet select the TCP/IP interface for your computers network card. Be careful not to select your wireless Ethernet connection.

To get it working quickly it is best to select the interface with the Auto designation. This will discover working settings and use them automatically.

For the PC Adapter click on the Properties button and make sure the Station Parameters Address is a unique network address. It should not conflict with existing PLC and slave devices on the network. Also, check under the Local Connection tab and make sure connection selection matches the port the cable is connected into.

Once the proper interface is selected and the properties are set then click OK and use the Accessible Nodes window to check for successful communications. It should work. If not double-check the connection and cable. With the CP5512 and PC Adapter cables, you should use the MPI port, as this is the default connection for Siemens.

If this doesn't work then I don't know what to tell you.


First, in order to enable the download menu commands, you must select the Block folder in the project's station you wish to download.

There are three methods of downloading.

  1. Partial download of selected blocks
  2. Full download of all blocks and system data
  3. Complete deletion of online PLC blocks and then downloading of all blocks and system data

Partial Download

Partial downloads are used in existing projects where only one or more blocks will be downloaded. To perform this type of download select the block(s) you wish to download and then select the PLC > Download menu item or the download button .

Holding down the Ctrl key or the Shift key allows more then one block to be selected at a time. Be careful though as the order of download will occur in the order that the blocks were selected. This may mean that an error will occur if a block is called before it is downloaded.

The CPU will need to be in Stop mode before downloading the System Data Block (SDB) as this is equivalent to a hardware configuration download. This is usually not necessary in a PLC that has all ready had its hardware configured. If you do download the system data, the following messages will prompt you through the transitions.

If the CPU is in Run mode then you will be prompted to Stop the CPU. The software will do the Run to Stop transition when you click OK.

After downloading the SDB you will be prompted to Run the CPU again.

Clicking Yes will automatically put the CPU back into run mode.

Full Download

To download all the blocks at once make sure you are in the Block folder and select the Edit > Select All menu item. Click on the Download icon . You will be prompted to overwrite any existing blocks and if you want to load the system data (see above).

Clearing the CPU Memory and then Downloading

The partial and full download methods above will overwrite existing blocks but will not any blocks from memory. In order to completely delete the existing program in the CPU and download a new project select the Blocks folder and then use the PLC > Download User Program to Memory Card menu item.

The following dialog box will pop up prompting you about the deletion of all the blocks and project data in the PLC. Click Yes to perform the operation.

After this, follow the normal download procedure.


There are two methods for uploading. The first is when you have the original project and you want to preserve the symbols and comments. The second method, when you don't have the original project, will upload everything from the CPU but will have no associated documentation (i.e. symbols and comments).

Uploading to an Existing Project

With the existing project open, select the View > Online menu item.

This is the same as the Online button on the icon bar.

This will open up another window called the Online Partner. It shows the existing blocks inside the CPU. The Online version is indicated by the highlighted title bar.

There is a connection between these two versions so that uploading from the online partner makes sure to preserve all the symbols and comments. Be careful. After uploading, make sure to close the online partner and do all work from the offline version.

To upload individual blocks, select them in the Online view and choose the PLC > Upload to PG menu item. For a full upload, select the Block folder and do the same.

Upload without an Existing Project

Follow these steps when you do not have the original project but wish to upload the program for backup purposes. With an existing project open or a new blank project select the PLC > Upload Station to PG… menu selection.

In the next screen, fill in the slot the CPU is in (this is always 2 for S7-300) and the node address of the communication port on the CPU. In the case below we are talking to a CPU over MPI with node address 10.

After clicking OK, the whole contents of the PLC including all blocks and hardware configuration will be uploaded into a new station in the project.

While this project contains no documentation, it can be used as a backup to download later if needed.

Step 7 Lite, Step 7 and Step 7 Professional Differences


STEP 7 Lite


STEP 7 Professional





Digital, analog I/O, IFM
centralized only

Digital, analog I/O, IFM, FM, CP
centralized and distributed (DP)



Time-driven, cyclic data transmission between automation components;
MPI, PROFIBUS or Industrial Ethernet

Distributed I/O



Alarm configuring (display->HMI)



Write/read to/from MMC

Yes, in CPU only

Yes, in CPU and direct on PG/PC
(updating of PLC operating system possible)


Program, symbols

Program, symbols, hardware configuration

Documentation function


Included - S7-DOCPRO option for standard-compliant documentation of the S7 project

Multi-language documentation of projects



Multi-user engineering





LAD/FBD/STL and STL sources

As Step 7
 + S7-Graph (sequencer)/S7-SCL (textual high-level language)

Structured/symbolic programming



Check/establish program consistency



Standard libraries/user libraries



Online functions
Online access


MPI, Profibus, Option: Industrial Ethernet

Test functions

Monitor, control, force

Monitor, control, force, single step (debug)

Comparison function offline/online

Program, hardware configuration



System diagnostics

System diagnostics, report system fault, integrated process fault diagnostics in S7-Graph

Optional packages
Optional programming languages


S7-Graph, S7-SCL, S7-HiGraph, CFC

S7-HiGraph, CFC

Options for simulation, documentation, diagnostics and remote maintenance

S7-PLCSIM, S7-Teleservice

S7-PLCSIM, S7-Teleservice, S7-DOCPRO, S7-Pdiag

S7-Teleservice, S7-DOCPRO, S7-Pdiag
(S7-PLCSIM is all ready included in package)

The Case of the Missing SIMATIC Step 7 Documentation

“We had documentation at one time.”

Sound familiar?  Have you suddenly found changes that have been made in the PLC but not in the offline program?  Nobody knows what happened.

Unfortunately this is an all too common phenomena with the Siemens SIMATIC Step 7 software.  The problems stem from the flexibility of the software both for downloading and editing the online program.  If the person is not familiar with the software it’s very easy to get confused if the changes are being made on the computer or in the controller.

How to solve this problem?  Let’s first of all review some basic terminology.  After that is a step by step best practice when editing programs.  Finally, we’ll highlight the pitfalls and the indicators that tell you whether you are offline or online.  This procedure applies to SIMATIC Step 7 version 5.4.


Offline program – The program that is stored on the hard disk of the computer.  This will contain the documentation.  It’s very important to keep a pristine copy of the offline program as the associated documentation is not stored in the PLC.

Online program – This is the program resident in the PLC. 

Download – The act of taking the offline program on the computer and downloading it into the PLC.

Upload – Taking the program in the PLC and bringing it up to the computer.  Doing this without having the associated offline program open will cause a loss of documentation.


Siemens Upload Download Direction


Save – Stores the open block onto the hard drive.  It’s important to realize that an edited block can be downloaded to the PLC without saving it offline.  Note that this only saves the opened block and not any others that are concurrently open.

These may seem like simple terms but it’s important to understand how they’re used in the Siemens environment.

Here are some other terms that may come up.

PG/PC – This is Siemens way of referring to a PC or laptop running the SIMATIC software.

Nodes – Refers to any programmable device (in our case a PLC) in the network which will have its own unique address.

Best Practice

The best practice is to make sure you are working from an offline file.  There really isn’t any reason to be working on the program inside the PLC.  Of course, this assumes that you have a good working copy to begin with.  The “golden” copy of the program should live somewhere on a network server or have a dedicated place on one computer or laptop.  I’ve even heard of some companies using USB memory sticks to store the latest and greatest which is great but an original copy should still live on a computer that is backed up.

  1. Open the offline file from the File pull down menu and select Open or use the  Open Project icon  Siemens Project Open Icon on the toolbar.  In the dialog box select the project under the User Project tab. Click OK.  You may have to select Browse to find it in the directory structure.  Note if the Manager was closed with a project open then it will open back up to that project automatically.
  2. Expand the project tree down to the program files and select the Blocks folder.  Good practice dictates that all blocks should be opened from here.
  3. Once changes have been made:
    1. Save the block to the hard disk by clicking the Save icon Siemens Project Open Icon (or menu item File | Save)
    2. Download the block by clicking the Download icon Siemens Project Open Icon (or menu item PLC | Download).  If the block all ready exists in the PLC then it will confirm that you want to overwrite it1.  Click Yes.
    3. Note that downloading from here only sends that one block to the PLC.  It does not download the entire program.
  4. To monitor the block make sure to open it using steps 1 through 3 and then press the Monitor icon Siemens Project Open Icon (or menu item Debug | Monitor).  The window’s title bar will highlight a lovely shade of blue to indicate a connection to the CPU.  It’s important to note here that you are still working with the program on the computer and not the PLC.  If the procedure in step 3 has not been followed then discrepancies can occur between what you are monitoring in the PLC and what is displayed in the SIMATIC software.

That’s it.  Following these simple steps will save a lot of headaches.


Pitfalls Ahead


The Pitfalls and Warning Signs

So where do some people get lost?  Here are some common mistakes and their warning signs.  If you get any of these dialog boxes then you should really back out and start over because you’re on the road to losing your documentation.

Siemens Missing 01


Siemens Missing 02
These dialog boxes are telling you that it cannot find the documentation for the local parameters and symbols.  More then likely it will also not show any network comments or titles.

The result of opening the block looks like this


Siemens Missing 03


This is an example void of documentation.  Notice the local parameters all say TEMP.  There are no comments or titles.  There are no symbols so it’s all in direct addressing.  The properly documented copy looks like this...


Siemens Missing 04


Pitfall #1 – Using Accessible Nodes to Open Blocks

The  Display Accessible Nodes Siemens Project Open Icon selection under the PLC menu is a handy way to see what is connected to the network but it should never be used to open blocks.  Opening blocks from here uploads it straight from the PLC and produces the warnings dialog boxes shown above.

Siemens Accessible Nodes Menu


Siemens Accessible Nodes Window


Pitfall #2 – Viewing Online from SIMATIC manager

Once a project is open and a connection to a PLC is established then selecting the Online button Siemens Project Open Icon (menu View | Online) brings up a similar project tree showing the contents inside the PLC.  The window title bar is highlighted in blue to indicate its online status.  Working from this window presents less of a danger for losing documentation but it is confusing and could lead to problems.  For instance if a block is renamed offline and then the old one is opened online then it will have no associated documentation.

The proper way to view a block online is to open the block and select the Establish Connection to Configured CPU icon Siemens Project Open Icon.  Just make sure what you are viewing has been downloaded to the PLC.


Siemens Online Partner Window


Pitfall #3 – Opening the Online Partner

If an offline block is open then selecting the  Open Offline/Online Partner icon Siemens Project Open Icon (menu item File | Open Online) will switch it to the online version of the block for editing.  Essentially this puts you in the same place as pitfall #2.


Programming with SIMATIC Step 7 is different enough from other types of PLCs to throw off the casual user.  Always working from the offline copy will make it less likely to screw up.  Opening up a block from the accessible nodes window is always a no-no.  Likewise, opening a block from a window that has a highlighted blue title bar will also cause potential problems.  Be sure and read all dialog boxes especially the ones we’ve shown in the article.  Avoid the pitfalls and keep that documentation.  Mystery solved.



(1) Siemens dialog boxes have an option that says, “Do not display this message again.”  This is handy for some annoying pop ups but it is really not a good idea to turn off important ones like warnings for overwriting blocks.  These warnings are especially crucial if you are working on real machinery.  If more then one person is using the software then you can reset these messages to display again by going to the SIMATIC Manager and select the menu Options | Customize.  Click the General tab and press the Activate button.  If it’s grayed out then all messages are set to display.

S7 Library Functions

I couldn't find a complete listing of all the function blocks in the standard Siemens S7 Libraries so I made one myself. It helps me get a better overview of what is available. The complete listing is also available as an Excel spreadsheet so you can sort or adjust to your needs.

System Function Blocks

Number Name Family Description
SFB 1 CTD IEC_TC Count Down
SFB 2 CTUD IEC_TC Count Up/Down
SFB 3 TP IEC_TC Generate a Pulse
SFB 4 TON IEC_TC Generate an On Delay
SFB 5 TOF IEC_TC Generate an Off Delay
SFB 8 USEND COM_FUNC Uncoordinated Sending of Data
SFB 9 URCV COM_FUNC Uncoordinated Receiving of Data
SFB 12 BSEND COM_FUNC Sending Segmented Data
SFB 13 BRCV COM_FUNC Receiving Segmented Data
SFB 14 GET COM_FUNC Read Data from a Remote CPU
SFB 15 PUT COM_FUNC Write Data to a Remote CPU
SFB 16 PRINT COM_FUNC Send Data to Printer
SFB 19 START COM_FUNC Initiate a Warm or Cold Restart on a Remote Device
SFB 20 STOP COM_FUNC Changing a Remote Device to the STOP State
SFB 21 RESUME COM_FUNC Initiate a Hot Restart on a Remote Device
SFB 22 STATUS COM_FUNC Query the Status of a Remote Partner
SFB 23 USTATUS COM_FUNC Receive the Status of a Remote Device
SFB 29 HS_COUNT COUNTERS Counter (high-speed counter, integrated function) (only exist on the CPU 312 IFM and CPU 314 IFM)
SFB 30 FREQ_MES COUNTERS Frequency Meter (frequency meter, integrated function (only exist on the CPU 312 IFM and CPU 314 IFM)
SFB 31 NOTIFY_8P COM_FUNC Generating block related messages without acknowledgement indication
SFB 32 DRUM TIMERS Implement a Sequencer
SFB 33 ALARM COM_FUNC Generate Block-Related Messages with Acknowledgment Display
SFB 34 ALARM_8 COM_FUNC Generate Block-Related Messages without Values for 8 Signals
SFB 35 ALARM_8P COM_FUNC Generate Block-Related Messages with Values for 8 Signals
SFB 36 NOTIFY COM_FUNC Generate Block-Related Messages without Acknowledgment Display
SFB 37 AR_SEND COM_FUNC Send Archive Data
SFB 38 HSC_A_B COUNTERS Counter A/B (integrated function) (only exist on the CPU 314 IFM)
SFB 39 POS ICONT Position (integrated function) (only exist on the CPU 314 IFM)
SFB 41 CONT_C ICONT Continuous Control (only exist on the CPU 314 IFM)
SFB 42 CONT_S ICONT Step Control (only exist on the CPU 314 IFM)
SFB 43 PULSEGEN ICONT Pulse Generation (only exist on the CPU 314 IFM)
SFB 44 ANALOG TEC_FUNC Positioning with Analog Output (only exist on the S7-300C CPUs)
SFB 46 DIGITAL TEC_FUNC Positioning with Digital Output (only exist on the S7-300C CPUs)
SFB 47 COUNT TEC_FUNC Controlling the Counter (only exist on the S7-300C CPUs)
SFB 48 FREQUENC TEC_FUNC Controlling the Frequency Measurement (only exist on the S7-300C CPUs)
SFB 49 PULSE TEC_FUNC Controlling Pulse Width Modulation (only exist on the S7-300C CPUs)
SFB 52 RDREC DP Reading a Data Record
SFB 53 WRREC DP Writing a Data Record
SFB 54 RALRM DP Receiving an Interrupt
SFB 60 SEND_PTP TEC_FUNC Sending Data (ASCII, 3964(R)) (only exist on the S7-300C CPUs)
SFB 61 RECV_PTP TEC_FUNC Receiving Data (ASCII, 3964(R)) (only exist on the S7-300C CPUs)
SFB 62 RES_RECV TEC_FUNC Deleting the Receive Buffer (ASCII, 3964(R)) (only exist on the S7-300C CPUs)
SFB 63 SEND_RK TEC_FUNC Sending Data (RK 512) (only exist on the S7-300C CPUs)
SFB 64 FETCH_RK TEC_FUNC Fetching Data (RK 512) (only exist on the S7-300C CPUs)
SFB 65 SERVE_RK TEC_FUNC Receiving and Providing Data (RK 512) (only exist on the S7-300C CPUs)
SFB 75 SALRM DP Send interrupt to DP master
SFB 81 RD_DPAR IO_FUNCT Read Predefined Parameter

System Function Calls

Number Name Family Description
SFC 0 SET_CLK CLK_FUNC Set System Clock
SFC 1 READ_CLK CLK_FUNC Read System Clock
SFC 2 SET_RTM CLK_FUNC Set Run-time Meter
SFC 3 CTRL_RTM CLK_FUNC Start/Stop Run-time Meter
SFC 4 READ_RTM CLK_FUNC Read Run-time Meter
SFC 5 GADR_LGC IO_FUNCT Query Logical Address of a Channel
SFC 6 RD_SINFO DB_FUNCT Read OB Start Information
SFC 7 DP_PRAL DP Trigger a Hardware Interrupt on the DP Master
SFC 9 EN_MSG COM_FUNC Enable Block-Related, Symbol-Related and Group Status Messages
SFC 10 DIS_MSG COM_FUNC Disable Block-Related, Symbol-Related and Group Status Messages
SFC 11 DPSYC_FR DP Synchronize Groups of DP Slaves
SFC 12 D_ACT_DP DP Deactivation and activation of DP slaves
SFC 13 DPNRM_DG DIAGNSTC Read Diagnostic Data of a DP Slave (Slave Diagnostics)
SFC 14 DPRD_DAT DP Read Consistent Data of a Standard DP Slave
SFC 15 DPWR_DAT DP Write Consistent Data to a DP Standard Slave
SFC 17 ALARM_SQ PMC_FUNC Generate Acknowledgeable Block-Related Messages
SFC 18 ALARM_S PMC_FUNC Generate Permanently Acknowledged Block-Related Messages
SFC 19 ALARM_SC PMC_FUNC Query the Acknowledgment Status of the last ALARM_SQ Entering State Message
SFC 20 BLKMOV MOVE Copy Variables
SFC 21 FILL MOVE Initialize a Memory Area
SFC 22 CREAT_DB DB_FUNCT Create Data Block
SFC 23 DEL_DB DB_FUNCT Delete Data Block
SFC 24 TEST_DB DB_FUNCT Test Data Block
SFC 25 COMPRESS DB_FUNCT Compress the User Memory
SFC 26 UPDAT_PI IO_FUNCT Update the Process Image Update Table
SFC 27 UPDAT_PO IO_FUNCT Update the Process Image Output Table
SFC 28 SET_TINT PGM_CNTL Set Time-of-Day Interrupt
SFC 29 CAN_TINT PGM_CNTL Cancel Time-of-Day Interrupt
SFC 30 ACT_TINT PGM_CNTL Activate Time-of-Day Interrupt
SFC 31 QRY_TINT PGM_CNTL Query Time-of-Day Interrupt
SFC 32 SRT_DINT PGM_CNTL Start Time-Delay Interrupt
SFC 33 CAN_DINT PGM_CNTL Cancel Time-Delay Interrupt
SFC 34 QRY_DINT PGM_CNTL Query Time-Delay Interrupt
SFC 35 MP_ALM PGM_CNTL Trigger Multicomputing Interrupt
SFC 36 MSK_FLT DIAGNSTC Mask Synchronous Errors
SFC 37 DMSK_FLT DIAGNSTC Unmask Synchronous Errors
SFC 38 READ_ERR DIAGNSTC Read Error Register
SFC 39 DIS_IRT IRT_FUNC Disable New Interrupts and Asynchronous Errors
SFC 40 EN_IRT IRT_FUNC Enable New Interrupts and Asynchronous Errors
SFC 41 DIS_AIRT IRT_FUNC Delay Higher Priority Interrupts and Asynchronous Errors
SFC 42 EN_AIRT IRT_FUNC Enable Higher Priority Interrupts and Asynchronous Errors
SFC 43 RE_TRIGR PGM_CNTL Re-trigger Cycle Time Monitoring
SFC 44 REPL_VAL DIAGNSTC Transfer Substitute Value to Accumulator 1
SFC 46 STP PGM_CNTL Change the CPU to STOP
SFC 47 WAIT PGM_CNTL Delay Execution of the User Program
SFC 48 SNC_RTCB CLK_FUNC Synchronize Slave Clocks
SFC 49 LGC_GADR IO_FUNCT Query the Module Slot Belonging to a Logical Address
SFC 50 RD_LGADR IO_FUNCT Query all Logical Addresses of a Module
SFC 51 RDSYSST DIAGNSTC Read a System Status List or Partial List
SFC 52 WR_USMSG DIAGNSTC Write a User-Defined Diagnostic Event to the Diagnostic Buffer
SFC 54 RD_PARM IO_FUNCT Read Defined Parameters
SFC 55 WR_PARM IO_FUNCT Write Dynamic Parameters
SFC 56 WR_DPARM IO_FUNCT Write Default Parameters
SFC 57 PARM_MOD IO_FUNCT Assign Parameters to a Module
SFC 58 WR_REC IO_FUNCT Write a Data Record
SFC 59 RD_REC IO_FUNCT Read a Data Record
SFC 60 GD_SND COM_FUNC Send a GD Packet
SFC 61 GD_RCV COM_FUNC Fetch a Received GD Packet
SFC 62 CONTROL COM_FUNC Query the Status of a Connection Belonging to a Communication SFB Instance
SFC 63 AB_CALL PLASTICS Assembly Code Block (only exists for CPU 614)
SFC 64 TIME_TCK CLK_FUNC Read the System Time
SFC 65 X_SEND COM_FUNC Send Data to a Communication Partner outside the Local S7 Station
SFC 66 X_RCV COM_FUNC Receive Data from a Communication Partner outside the Local S7 Station
SFC 67 X_GET COM_FUNC Read Data from a Communication Partner outside the Local S7 Station
SFC 68 X_PUT COM_FUNC Write Data to a Communication Partner outside the Local S7 Station
SFC 69 X_ABORT COM_FUNC Abort an Existing Connection to a Communication Partner outside the Local S7 Station
SFC 70 GEO_LOG IO_FUNCT Determine Start Address of a Module
SFC 71 LOG_GEO IO_FUNCT Determine the Slot Belonging to a Logical Address
SFC 72 I_GET COM_FUNC Read Data from a Communication Partner within the Local S7 Station
SFC 73 I_PUT COM_FUNC Write Data to a Communication Partner within the Local S7 Station
SFC 74 I_ABORT COM_FUNC Abort an Existing Connection to a Communication Partner within the Local S7 Station
SFC 78 OB_RT DIAGNSTC Determine OB program runtime
SFC 79 SET BIT_LOGC Set a Range of Outputs
SFC 80 RSET BIT_LOGC Reset a Range of Outputs
SFC 81 UBLKMOV MOVE Uninterruptible Block Move
SFC 82 CREA_DBL DB_CTRL Create a Data Block in the Load Memory
SFC 83 READ_DBL DB_CTRL Read from a Data Block in Load Memory
SFC 84 WRIT_DBL DB_CTRL Write from a Data Block in Load Memory
SFC 85 CREA_DB DB_FUNCT Create a Data Block
SFC 87 C_DIAG COM_FUNC Diagnosis of the Actual Connection Status
SFC 90 H_CTRL HF_FUNCT Control Operation in H Systems
SFC 100 SET_CLKS CLK_FUNC Setting the Time-of-Day and the TOD Status
SFC 101 RTM CLK_FUNC Handling runtime meters
SFC 102 RD_DPARA IO_FUNCT Redefined Parameters
SFC 103 DP_TOPOL DP Identifying the bus topology in a DP master system
SFC 104 CIR PGM_CNTL Controlling CiR
SFC 105 READ_SI PMC_FUNC Reading Dynamic System Resources
SFC 106 DEL_SI PMC_FUNC Deleting Dynamic System Resources
SFC 107 ALARM_DQ PMC_FUNC Generating Always Acknowledgeable and Block-Related Messages
SFC 108 ALARM_D PMC_FUNC Generating Always Acknowledgeable and Block-Related Messages
SFC 112 PN_IN PROFIne2 Update inputs in the user program interface of PROFInet components
SFC 113 PN_OUT PROFIne2 Update outputs in the user program interface of PROFInet components
SFC 114 PN_DP PROFIne2 Update DP interconnections
SFC 126 SYNC_PI IO_FUNCT Update process image partition input table in synchronous cycle
SFC 127 SYNC_PO IO_FUNCT Update process image partition output table in synchronous cycle

S5-S7 Converting Blocks

Number Name Family Description
FC 61 GP_FPGP S5_CNVRT Change fixed point number to floating point number
FC 62 GP_GPFP S5_CNVRT Change floating point number to fixed point number
FC 63 GP_ADD S5_CNVRT Add floating point numbers
FC 64 GP_SUB S5_CNVRT Subtract floating point numbers
FC 65 GP_MUL S5_CNVRT Multiply floating point number
FC 66 GP_DIV S5_CNVRT Divide floating point numbers
FC 67 GP_VGL S5_CNVRT Compare floating point numbers
FC 68 RAD_GP S5_CNVRT Extract root of floating point numbers
FC 69 MLD_TG S5_CNVRT Clock generator
FC 70 MLD_TGZ S5_CNVRT Clock generator (timing element)
FC 71 MLD_EZW S5_CNVRT Message of first value with single flashing light, wordwise, A
FC 72 MLD_EDW S5_CNVRT Message of first value with double flashing light, wordwise, A
FC 73 MLD_SAMW S5_CNVRT Collected message, wordwise (sound alert)
FC 74 MLD_SAM S5_CNVRT Collected message, bitwise
FC 75 MLD_EZ  S5_CNVRT Message of first value with single flashing light, bitwise, A
FC 78 MLD_EDWK S5_CNVRT Message of first value with double flashing light, wordwise, A+M
FC 79 MLD_EZK S5_CNVRT Message of first value with single flashing light, bitwise, A+M
FC 80 MLD_EDK S5_CNVRT Message
of first value with double flashing light, bitwise, A+M
FC 81 COD_B4 S5_CNVRT Change BCD number to 16 bit dual number
FC 82 COD_16 S5_CNVRT Change 16 bit dual number to BCD number
FC 83 MUL_16 S5_CNVRT Multiply 16 bit dual numbers
FC 84 DIV_16 S5_CNVRT Divide 16 bit dual numbers
FC 85 ADD_32 S5_CNVRT Add 32 bit dual numbers
FC 86 SUB_32 S5_CNVRT Subtract 32 bit dual numbers
FC 87 MUL_32  S5_CNVRT Multiply 32 bit dual numbers
FC 88 DIV_32 S5_CNVRT Divide 32 bit dual numbers
FC 89 RAD_16 S5_CNVRT Extract roots of 16 bit dual numbers
FC 90 REG_SCHB S5_CNVRT Bi-directional shift register, bitwise
FC 91 REG_SCHW  S5_CNVRT Bi-directional shift register, wordwise
FC 92 REG_FIFO S5_CNVRT Buffer memory (FIFO)
FC 93 REG_LIFO S5_CNVRT Stack register (LIFO)
FC 94 DB_COPY1 S5_CNVRT Copy data block, direct assignment of parameters
FC 95 DB_COPY2  S5_CNVRT Copy data block, indirect assignment of parameterization
FC 96 RETTEN S5_CNVRT Save scratchpad memory
FC 97 LADEN S5_CNVRT Load scratchpad memory
FC 98 COD_B8 S5_CNVRT Change BCD number to 32 bit dual number
FC 99 COD_32 S5_CNVRT Change 32 bit dual number to BCD number
FC 100 AE_460_1 S5_CNVRT Read analog value
FC 101 AE_460_2 S5_CNVRT Read analog value
FC 102 AE_463_1 S5_CNVRT Read analog value
FC 103 AE_463_2 S5_CNVRT Read analog value
FC 104 AE_464_1 S5_CNVRT Read analog value
FC 105 AE_464_2 S5_CNVRT Read analog value
FC 106 AE_466_1 S5_CNVRT Read analog value
FC 107 AE_466_2 S5_CNVRT Read analog value
FC 108 RLG_AA1 S5_CNVRT Output analog value
FC 109 RLG_AA2 S5_CNVRT Output analog value
FC 110 PER_ET1 S5_CNVRT Read and Write for extended periphery (direct assignment of parameters)
FC 111 PER_ET2 S5_CNVRT Read and Write for extended periphery (indirect assignment of parameters)
FC 112 SINUS S5_CNVRT Sine (x)
FC 113 COSINUS S5_CNVRT Cosine (x)
FC 114 TANGENS S5_CNVRT Tangent (x)
FC 115 COTANG S5_CNVRT Cotangent (x)
FC 116 ARCSIN S5_CNVRT Arc sine (x)
FC 117 ARCCOS S5_CNVRT Arc cosine (x)
FC 118 ARCTAN S5_CNVRT Arc tangent (x)
FC 119 ARCCOT S5_CNVRT Arc cotangens (x)
FC 120 LN_X S5_CNVRT Natural logarithm ln (x)
FC 121 LG_X S5_CNVRT Decade logarithm Iog (x)
FC 122 B_LOG_X S5_CNVRT General logarithm log (x) to basis b
FC 123 E_H_N S5_CNVRT e to the power of n
FC 124 ZEHN_H_N S5_CNVRT 10 to the power of n
FC 125 A2_H_A1 S5_CNVRT AKKU 2 to the power of AKKU 1

IEC Function Blocks

Number Name Family Description
FC 1 AD_DT_TM IEC Point Math Add duration to a time
FC 2 CONCAT IEC Combine two STRING variables
FC 4 DELETE IEC Delete in a STRING variable
FC 5 DI_STRNG IEC Data type conversion DINT to STRING
FC 6 DT_DATE IEC Extract the DATE from DT
FC 7 DT_DAY IEC Extract the day of the week from DT
FC 8 DT_TOD IEC Extract the TIME_OF_DAY from DT
FC 9 EQ_DT IEC Compare DT for equal
FC 10 EQ_STRNG IEC Compare STRING for equal
FC 11 FIND IEC Find in a STRING variable
FC 12 GE_DT IEC Compare DT for greater than or equal
FC 13 GE_STRNG IEC Compare STRING for greater than or equal
FC 14 GT_DT IEC Compare DT for greater than
FC 15 GT_STRNG IEC Compare STRING for greater than
FC 16 I_STRNG IEC Data type conversion INT to STRING
FC 17 INSERT IEC Insert in a STRING variable
FC 18 LE_DT IEC Compare DT for smaller than or equal
FC 19 LE_STRNG IEC Compare STRING for smaller than or equal
FC 20 LEFT IEC Left part of a STRING variable
FC 21 LEN IEC Length of a STRING variable
FC 22 LIMIT IEC Point Math Limit
FC 23 LT_DT IEC Compare DT for smaller than
FC 24 LT_STRNG IEC Compare STRING for smaller than
FC 25 MAX IEC Point Math Select maximum
FC 26 MID IEC Middle part of a STRING variable
FC 27 MIN IEC Point Math Select minimum
FC 28 NE_DT IEC Compare DT for unequal
FC 29 NE_STRNG IEC Compare STRING for unequal
FC 30 R_STRNG IEC Data type conversion REAL to STRING
FC 31 REPLACE IEC Replace in a STRING variable
FC 32 RIGHT IEC Right part of a STRING variable
FC 33 S5TI_TIM IEC Data type conversion S5TIME to TIME
FC 34 SB_DT_DT IEC Point Math Subtract two time values
FC 35 SB_DT_TM IEC Point Math Subtract duration from a time
FC 36 SEL IEC Point Math Binary selection
FC 37 STRNG_DI IEC Data type conversion STRING to DINT
FC 38 STRNG_I IEC Data type conversion STRING to INT
FC 39 STRNG_R IEC Data type conversion STRING to REAL
FC 40 TIM_S5TI IEC Data type conversion TIME to S5TIME

PID Control Blocks

Number Name Family Description
FB 41 CONT_C ICONT Continuous Control
FB 42 CONT_S ICONT Step Control
FB 43 PULSEGEN ICONT Pulse Generation
FB 58 TCONT_CP CONTROL Temperature Continuous Controller
FB 59 TCONT_S CONTROL Temperature Step Controller

Communication Blocks

Number Name Family Description
FB 2 IDENTIFY CP_300 For checking device
FB 3 READ CP_300 Reads data from a data area of the communication partner specified by a name or index depending on the assignment of parameters for the job.
FB 4 REPORT CP_300 Allows unconfirmed transmission of variables by an FMS server.
FB 5 STATUS CP_300 allows status information to be requested from the communications partner on the specified FMS connection.
FB 6 WRITE CP_300 Transfers data from a specified local data area to a data area on the communication partner.
FB 8 USEND CP_300 Uncoordinated Sending of Data
FB 9 URCV CP_300 Uncoordinated Receiving of Data
FB 12 BSEND CP_300 Sending Segmented Data
FB 13 BRCV CP_300 Receiving Segmented Data
FB 14 GET CP_300 Read Data from a Remote CPU
FB 15 PUT CP_300 Write Data to a Remote CPU
FB 20 GETIO IO_FUNCT Read All Inputs of a DP Standard Slave/PROFINET IO Device
FB 21 SETIO IO_FUNCT Write All Outputs of a DP Standard Slave/PROFINET IO Device
FB 22 GETIO_PART IO_FUNCT Read a Part of the Inputs of a DP Standard Slave/PROFINET IO Device
FB 23 SETIO_PART IO_FUNCT Write a Part of the Outputs of a DP Standard Slave/PROFINET IO Device
FB 55 IP_CONFIG CP_300 Transfers a configuration data block (CONF_DB) containing connection data for an Ethernet CP.
FB 63 TSEND COMM Sending Data via TCP native and ISO on TCP
FB 64 TRCV COMM Receiving Data via TCP native and ISO on TCP
FB 65 TCON COMM Establishing a Connection using TCP native and ISO on TCP
FB 66 TDISCON COMM Terminating a Connection using TCP native and ISO on TCP
FB 67 TUSEND COMM Sending Data via UDP
FB 68 TURCV COMM Receiving Data via UDP
FC 1 DP_SEND CP_300 transfers data to the PROFIBUS CP
FC 2 DP_RECV CP_300 receives data on PROFIBUS
FC 3 DP_DIAG CP_300 used to request diagnostic information
FC 4 DP_CTRL CP_300 transfers control jobs to the PROFIBUS CP
FC 5 AG_SEND CP_300 data by means of a configured connection to the communication partner (<= 240 bytes).
FC 6 AG_RECV CP_300 data by means of a configured connection from the communication partner (<= 240 bytes, not email).
FC 7 AG_LOCK CP_300 the external data access by means of FETCH/WRITE (not for UDP, email).
FC 8 AG_UNLOCK CP_300 the external data access by means of FETCH/WRITE (not for UDP, email).
FC 10 AG_CNTRL CP_300 allows you to diagnose connections. When necessary, you can reinitialize connection establishment using the FC.
FC 11 PNIO_SEND CP_300 used for data transfer in
the CP modes PROFINET IO controller or PROFINET IO device.
FC 12 PNIO_RECV CP_300 used to receive data in the CP modes PROFINET IO controller or PROFINET IO device.
FC 40 FTP_CONNECT CP_300 Establish an FTP connection
FC 41 FTP_STORE CP_300 Store a file on the FTP server
FC 42 FTP_RETRIEVE CP_300 Retrieve a file from the FTP server
FC 43 FTP_DELETE CP_300 Delete a file on the FTP server
FC 44 FTP_QUIT CP_300 Enable an FTP connection
FC 50 AG_LSEND CP_300 data by means of a configured connection to the communication partner.
FC 60 AG_LRECV CP_300 data by means of a configured connection from the communication partner (not email).
FC 62 C_CNTRL CP_300 Query a connection status for S7-300

TI-S7 Converting Blocks

Number Name Family Description
FB 80 LEAD_LAG CONVERT Lead/Lag Algorithm
FB 81 DCAT TIMERS Discrete Control Alarm Timer
FB 82 MCAT TIMERS Motor Control Alarm Timer
FB 83 IMC COMPARE Index Matrix Compare
FB 84 SMC COMPARE Scan Matrix Compare
FB 85 DRUM TIMERS Event Maskable Drum
FB 86 PACK MOVE Pack Data
FC 80 TONR TIMERS Software Timer On Delay—Retentive
FC 81 IBLKMOV MOVE Indirect Block Move
FC 82 RSET BIT_LOGC Reset Range of Outputs
FC 83 SET BIT_LOGC Set Range of Outputs
FC 84 ATT TABLE Add to Table
FC 85 FIFO TABLE First In/First Out Unload Table
FC 87 LIFO TABLE Last In/First Out Unload Table
FC 89 TBL_WRD TABLE Move Table to Word
FC 90 WSR SHIFT Word Shift Register
FC 91 WRD_TBL TABLE Word to Table
FC 92 SHRB SHIFT Bit Shift Register
FC 93 SEG CONVERT Seven Segment Decoder
FC 96 ENCO CONVERT Encode Binary Position
FC 97 DECO CONVERT Decode Binary Position
FC 98 BCDCPL CONVERT Ten’s Complement
FC 99 BITSUM CONVERT Sum Number of Bits
FC 100 RSETI BIT_LOGC Reset Range of Immediate Outputs
FC 101 SETI BIT_LOGC Set Range of Immediate Outputs
FC 102 DEV MATH_FP Standard Deviation
FC 103 CDT TABLE Correlated Data Table
FC 104 TBL_TBL TABLE Table to Table
FC 105 SCALE CONVERT Scaling Values
FC 106 UNSCALE CONVERT Unscaling Values

Miscellaneous Blocks

Number Name Family Description
FB 60 SET_SW TIMEFUNC supports the summertime/wintertime changeover in CPUs that do not have the time status. For this purpose it sets the CPU clock to the current time and according to the changeover rules in the Control DB.
FB 61 SET_SW_S TIMEFUNC supports the summertime/wintertime changeover in CPUs that do have the time status. For this purpose it sets the time status to the current time and according to the changeover rules in the Control DB.
FB 62 TIMESTMP TIMEFUNC transfers the time-stamped messages of an IM153-2 into its instance DB.
FC 60 LOC_TIME TIMEFUNC reads the time status or time of the CPU and calculates the local time. It is therefore only useful on CPUs with time status.
FC 61 BT_LT TIMEFUNC calculates the local time from the base time given at the input.
FC 62 LT_BT TIMEFUNC calculates the base time from the local time given at the input.
FC 63 S_LTINT TIMEFUNC sets the required time interrupt to the preset time. This time is given in local time.

Siemens Technical Terms

Otherwise known as Siemens speak. Here's a list of Siemens specific abbreviations and their meanings.


Term Description Explanation
C7 Combo PLC/HMI system A PLC and screen in one package
CFC Continuous Function Chart Optional programming language
CP Communication Processor Modules used for special communication protocols
DB Data Block Memory storage areas for user data
FB Function Block A function with it's own data block
FBD Function Block Diagram Standard programming language
FC Function Call Called progammed blocks
FM Function Module Modules with special functions (e.g. positioning)
GSD Generic Station Description Files used for Profibus descriptions
HiGraph   Optional programming language
IM Interface Module Modules to connect remote racks
LAD Ladder Logic Diagram Standard programming language
M7 Programmable modules A module with processing capabilities
MMC Micro Memory Card Compact plug-in memory card
MPI Multi Point Interface Standard communication protocol
OB Organization Block Blocks for user programs based on different operating system events.
OP Operator Panel Simple display with or without buttons
PCS Process Control System Software for the entire process chain
PG Programming Terminal Dedicated Siemens device - basically a PC
PPI Point to Point Interface Serial RS-232 communication
Profibus DP Profibus Decentral Peripherals Networking protocol used for factory automation
Profibus PA Profibus Process Automation Networking protocol used for process automation
S7   SIMATIC Step 7 product line
SCL Structured Control Language Optional programming language
SFB System Function Block Integrated FB for CPU information
SFC System Function Call Integrated FC for CPU information
SM Signal Module Standard Input/Output modules
STL Statement List Text based programming language
TP Touch Panel Touch screen display
UDT User-Definded Data Type Special data structures defined by the user
VAT Variable Access Table Tables used to monitor/modify values in the PLC


Step 7 Elementary Data Types

Type and
Format Options Range and Number Notation
(lowest to highest values)
Example in STL
BOOL (Bit) 1 Boolean text  TRUE/FALSE  TRUE
BYTE (Byte) 8 Hexadecimal number B#16#0 to B#16#FF  L B#16#10
L byte#16#10
WORD (Word) 16 Binary number 2#0 to 2#1111_1111_1111_1111 L 2#0001_0000_0000_0000
Hexadecimal number W#16#0 to W#16#FFFF L W#16#1000
L word#16#1000
BCD C#0 to C#999 L C#998
Decimal number unsigned B#(0,0) to B#(255,255) L B#(10,20)
L byte#(10,20)
DWORD (Double word) 32 Binary number 2#0 to 2#1111_1111_1111_1111_

L 2#1000_0001_0001_1000_

Hexadecimal number W#16#0000_0000 to W#16#FFFF_FFFF L DW#16#00A2_1234
L dword#16#00A2_1234
Decimal number unsigned B#(0,0,0,0) to B#(255,255,255,255) L B#(1, 14, 100, 120)
L byte#(1,14,100,120)
INT (Integer) 16 Decimal number signed -32768 to 32767 L 101
DINT (Double integer) 32 Decimal number signed L#-2147483648 to L#2147483647 L L#101
REAL (Floating-point number) 32 IEEE Floating-point number Upper limit +/-3.402823e+38
Lower limit +/-1.175495e-38
L 1.234567e+13
S5TIME (SIMATIC time) 16 S7 time in steps of 10ms (default) S5T#0H_0M_0S_10MS to
S5T#2H_46M_30S_0MS and
L S5T#0H_1M_0S_0MS
L S5TIME#0H_1H_1M_0S_0MS
TIME (IEC time) 32 IEC time in steps of 1 ms, integer signed T#24D_20H_31M_23S_648MS
L T#0D_1H_1M_0S_0MS
L TIME#0D_1H_1M_0S_0MS
DATE (IEC date) 16 IEC date in steps of 1 day D#1990-1-1 to
L D#1996-3-15
L DATE#1996-3-15
TIME _OF_DAY (Time) 32 Time in steps of 1 ms TOD#0:0:0.0 to
L TOD#1:10:3.3
L TIME_OF_DAY#1:10:3.3
CHAR (Character) 8 ASCII characters A', 'B' etc. L 'E'



  • Underscores in time and date are optional
  • It is not required to specify all time units (for example: T#5h10s is valid)
  • Maximum time value = 9,990 seconds or 2H_46M_30S

S5TIME Format

S5TIME Format


Time base Binary Code
10 ms 00
100 ms 01
1 s 10
10 s 11

Symbol Table Allowed Addresses and Data Types

Description Data Type Address Range
I/O Signals
I E Input bit BOOL 0 to 65535.7
IB EB Input byte BYTE, CHAR 0 to 65535
IW EW Input word WORD, INT, S5TIME, DATE 0 to 65534
ID ED Input double word DWORD, DINT, REAL, TOD, TIME 0 to 65532
Q A Output bit BOOL 0 to 65535.7
QB AB Output byte BYTE, CHAR 0 to 65535
QW AW Output word WORD, INT, S5TIME, DATE 0 to 65534
QD AD Output double word DWORD, DINT, REAL, TOD, TIME 0 to 65532
Marker Memory
M M Memory bit BOOL 0 to 65535.7
MB MB Memory byte BYTE, CHAR 0 to 65535
MW MW Memory word WORD, INT, S5TIME, DATE 0 to 65534
MD MD Memory double word DWORD, DINT, REAL, TOD, TIME 0 to 65532
Peripheral I/O
PIB PEB Peripheral input byte BYTE, CHAR 0 to 65535
PIW PEW Peripheral input word WORD, INT, S5TIME, DATE 0 to 65534
PID PED Peripheral input double word DWORD, DINT, REAL, TOD, TIME 0 to 65532
PQB PAB Peripheral output byte BYTE, CHAR 0 to 65535
PQW PAW Peripheral output word WORD, INT, S5TIME, DATE 0 to 65534
PQD PAD Peripheral output double word DWORD, DINT, REAL, TOD, TIME 0 to 65532
Timers and Counters
T T Timer TIMER 0 to 65535
C Z Counter COUNTER 0 to 65535
Logic Blocks
FB FB Function block FB 0 to 65535
OB OB Organization block OB 1 to 65535
FC FC Function FC 0 to 65535
SFB SFB System function block SFB 0 to 65535
SFC SFC System function SFC 0 to 65535
Data Blocks
DB DB Data block DB, FB, SFB, UDT 1 to 65535
User-defined data types
UDT UDT User-defined data type UDT 0 to 65535

Siemens S7 Indirect Addressing

by Automation Training

The following is provided by Automation Training from their excellent Siemens Step 7 training manual. This is a really nice explanation of a difficult but important subject. Check out their website for hands-on and online training classes.

Automation Training


The most common form of addressing used in the Siemens S7 PLCs is direct and symbolic. When a direct addressed is referenced by an instruction there is no question as to the location in memory. The following are examples of direct addressing:


I4.0, IB4, IW4 , ID4


Q124.0, QB124, QW124, QD124


M11.0, MB10, MW10, MD10






L0.0, LB1, LW2, LD4

Data Block:

DB5.DBX2.0, DB5.DBW6, DBD8

By using the methods of indirect addressing the address used by an instruction can be varied to point to any number of locations. In this case, a memory location stores a “pointer” to another memory location. While this may increase the difficulty of troubleshooting, its advantage is to greatly reduce the number of networks and instructions needed to control a process. It is also a method that must be understood to use some of the library and system function calls provided by Siemens.

The POINTER and ANY Data Types

A POINTER data type is used to format a number to be accepted as an address rather then a value. A pointer is always preceded by a P# symbol. The pointer address may be in three different formats.



Memory Storage



4 Bytes



6 Bytes


P#DB25.DBX0.0 BYTE 14
P#M0.0 WORD 2
P#I0.0 DWORD 5

10 Bytes

The ANY data type is used to pass a parameter of an unknown or undefined data type. Some functions in the library use the ANY data type to work on whole sections of memory. To do this, the last pointer method is used to describe an area. For example the address P#DB25.DBX 0.0 Byte 14 points to the first byte of DB25 with a length of 14 bytes.

NOTE: A DINT can be converted to a POINTER by simply shifting the double word left by 3 bits.

Data Block Instructions

When working with indirect addressing it is sometimes needed to first of all open a DB and then begin working on the
address without directly referring to any one DB. This is done using the OPN instruction. The OPN instruction can open either a shared data block (DB) or an instance data block (DI).

OPN DB 10 //Open DB10 as a shared data block
L DBW 36 //Load data word 36 of DB10 into ACCU1
T MW 22 //Transfer the contents of ACCU1 into MW22
OPN DI 20 //Open DB20 as an instance data block
L DIB 12 //Load data byte 12 from DB20 into ACCU1
T DBB 37 //Transfer the contents of ACCU1 to data
//byte 37 of the open shared data block DB10

When monitoring in STL the shared DB number is displayed in the DB1 column and the instance DB number is displayed in the DB2 column.

Furthermore, there are instructions to confirm that the correct DB number is opened and that it is large enough for the next operation.

L DBNO   //Loads the number of the opened
//shared data block into ACCU1
L DBLG   //Loads the length of the opened
//shared data block into ACCU1
L DINO   //Loads the number of the opened
//instance data block into ACCU1
L DILG   //Loads the length of the opened
//instance data block into ACCU1

Memory Indirect Addressing

The first method of indirect addressing is called memory indirect addressing because it allows for a memory location (M, DB or L) to determine or point to another.

The memory area identifiers T, C, DB, DI, FB and FC use a word (16-bit) pointer location in integer format. Two examples are as follows:

L 5   //Load ACCU1 with pointer value
T MW 2 //Transfer pointer into MW2
L T [MW 2] //Load ACCU1 with T5 current time value
OPN DB [#DB_Temp] //Open DB whose data block number is
//from the interface temp parameter
//named DB_Temp

The memory area identifiers I, Q, M, L, DB use a double word (32-bit) location using the POINTER data type.

L P#0.7   //Load ACCU1 with pointer value
T MD 2 //Transfer pointer into MD2
A I [MD 2] //Check state of I0.7
= M [MD 2] //Assign value of RLO to M0.7
OPN DB 5 //Open DB5
L P#2.0 //Load pointer into ACCU1
T #TempPointer //Transfer pointer to temp location
L DBW [#TempPointer] //Load the value at DB5.DBW2 into ACCU1
L 0 //Load a zero into ACCU1
>D   //Check if the value is greater
//then zero

When monitoring memory indirect addressing the INDIRECT column displays the current address the instruction is using.

Note that math can be done on the POINTER data type using the double math instructions (e.g. P#2.0 + P#5.0 = P#7.0).

L P#2.0   //Load ACCU1 with pointer value
L P#5.0   //Load ACCU1 with secondpointer value
T MD 0 //MD0 now contains the value P#7.0

Since the bit position only goes to eight the result of P#8.7 + P#1.1 = P#10.0 and not P#9.8. These methods can be used to offset the address or increase/decrease the pointer in a loop.

The Address Registers

Besides the regular accumulators, there are two 32-bit address registers (AR1, AR2) for storing pointers used in register indirect addressing methods. A series of different load and transfer type instructions can be used to work with AR1. A similar set is available for AR2.




Loads AR1 with the contents of ACCU1

LAR1 P#M100.0

Loads AR1 with a pointer constant


Loads AR1 with the pointer in MD24


Loads AR1 with the contents of AR2




Transfers the contents AR1 into ACCU1


Transfers the contents in AR1 to a memory location


Transfers the contents in AR1 to AR2




Exchanges the contents of AR1 with AR2

Addition can be directly accomplished on AR1 and AR2 with the following:




Adds the contents of ACCU1 to AR1 and stores the result back into AR1

+AR1 P#100.0

Adds the pointer constant to AR1 and stores the result back into AR1

Area-Internal Register Indirect Addressing

The area-internal register indirect addressing method uses one of the address registers plus a pointer to determine the address the instruction is to reference. The format is:

address identifier [address register, pointer]

The address identifier can be I, Q, M, L, DI or DB in bit, byte, word or double word form. The address register must be previously loaded with a double word pointer without reference to the address identifier. The exact address is determined by adding the address register with the pointer. The example below shows the area-internal method using bit locations.

L P#0.7   //Load ACCU1 with pointer value
LAR1     //Load AR1 with pointer in ACCU1
A I [AR1, P#0.0] //Check input I0.7
= Q [AR1, P#1.1] //If RLO=1 turn on Q2.0

Area-Crossing Register Indirect Addressing

Area-crossing register indirect addressing is similar to the area-internal method except the pointer loaded into the address register references a memory area (e.g. P#M10.0 or P#DBX0.0). This means the address identifier used before the opening bracket is not needed if referencing a bit otherwise it will be a B for byte, W for word or D for double. The example below shows the area-crossing method using bit locations.

L P#I0.7   //Load ACCU1 with pointer value
LAR1     //Load AR1 with pointer in ACCU1
L P#Q124.0   //Load ACCU1 with pointer value
LAR2     //Load AR2 with pointer in ACCU1
A [AR1, P#0.0] //Check input I0.7
= [AR2, P#1.1] //If RLO=1 turn on Q125.1

This next example shows area-crossing methods using a word and double word format.

L P#M0.0 //Load ACCU1 with pointer value
LAR1   //Load AR1 with pointer in ACCU1
L W [AR1, P#10.0] //Load the word whose address is
//determined by the contents of
//AR1 plus 10 bytes (MW10) into ACCU1
OPN DB 5 //Open DB5
L P#DBX 0.0 //Load ACCU1 with pointer value
LAR2   //Load AR2 with pointer in ACCU1
L L#0 //Load zero into ACCU1
T D [AR2, P#50.0] //Transfer the value in ACCU1 to the
//double word whose exact location is
//the address in AR2 plus 50 bytes

Exercise #1

  1. Comment the lines of STL below to describe what this network does:
  A I 0.0  
  JC M001  
  L P#M10.0  
  JU M002    
M001: L P#Q0.0  
M002: LAR1    
  A I 0.1  
  = [AR1, P#0.1]  
  1. Enter the code, monitor it and verify your answers.

Exercise #2 (Advanced)

  1. Create a DB with an array of 10 real numbers. Populate the array with random values.
  2. Create a function that will return the max number in the array and its position. Use the indirect addressing method of your choice.

Siemens S7 Status Word

In Siemens PLCs the Status Word is an internal CPU register used to keep track of the state of the instructions as they are being processed.  In order to use STL more effectively it is important to understand the Status Word and its functions.

Each bit in the Status Word has a specific function to keep track of bit logic (RLO, STA), math (OV, OS), comparison operations (CC0, CC1) and whether the logic should continue, be nested or start new (/FC, OR, BR).  Only the first 9 of the 16 bits are used.

Bit Positions



















Each instruction may do the following to each bit in the status word.


No read or write




May write "1" or "0"


Reset to "0"


Set to "1"

The status word can be seen by displaying the STATUS column while monitoring in STL view.  The RLO (bit 1) and the STA (bit 2) are also displayed in the RLO and STA column.

Status Word in STL Monitor

The Most Important Status Word Bits

/FC – First Check (bit 0)

If the /FC bit is a 0 then the instruction is considered to be the first instruction being processed.  If the /FC is a 1 then the instruction being scanned will use the logic from the previous instruction. Certain instructions like =, S and R will set the /FC bit to 0 thus starting new logic after it.  Other instructions like A or O will set the /FC bit to 1 signalling to combine the logic with the next instruction.

RLO – Result of Logic Operation (bit 1)

The RLO bit stores the running logic state of the currently processing instructions.  Certain bit logic and comparison instruction will turn the RLO to a 1 when the condition is TRUE and write a 0 when the condition is FALSE.  Other instructions read the RLO (=, S, R) to determine how they are to execute.

STA – Status (bit 2)

The STA bit reflects the state of the current Boolean address.

Help with RLO, STA and /FC

If you are used to ladder logic and struggling to understand the purpose of the RLO and STA it may help to visualize a rung like below.  The STA is used to keep track of the state of the addresses.  The RLO is used to keep track of the state of the rung.

Ladder Equivilant Monitored

The equivalent STL is shown below.

RLO and STA example.jpg

It steps through the logic as follows:

  1. At the start the First Check bit (/FC) is zero so an And instruction will logically mirror the Status bit (STA) over to the Result of Logic Operation (RLO).  In this case the address I0.0 is 1 so the STA is one and the result of the logic (RLO) will be 1.  The A instruction writes a 1 to /FC.
    rlo and sta example line 1.jpg
  2. On the second line, the /FC bit is now 1 indicating that this line needs to use the RLO from the previous line.  The address I1.1 is on so the STA = 1.  The RLO from the last line is 1 and this is ‘anded’ with the current STA with a result of 1 in the current RLO.
    rlo and sta example line 2.jpg
  3. The same thing happens on the second line but this time 1 and 0 makes the current RLO = 0.
    rlo and sta example line 3.jpg
  4. The fourth is the Assign instruction which takes the RLO and writes it out to the corresponding address.  In this case the final RLO = 0 so the output will be off.  If M0.0 was 1 then the “And” operation will evaluate to true making the RLO = 1 which will then turn on the output Q1.0.
    rlo and sta example line 4.jpg

The Other Status Bits

OR (bit 3)

The OR bit is used for combining AND functions before OR functions.

OS – Overflow Stored (bit 4)

In the event of an overflow (OV bit 5) the OS bit will store the value even after the OV bit has been reset.  The following commands reset the OS bit: JOS (Jump if OS=1), block call instructions, block end instructions.

OV – Overflow (bit 5)

The OV bit is set by a math instruction with floating point numbers after a fault has occurred (overflow, illegal operation, comparison unordered). The OV bit is reset when the fault is eliminated.

CC0, CC1 – Condition Code (bits 6 and 7)

The Condition Code bits provide results for comparison and math instructions.

Comparison Instructions

CC 1

CC 0













Unordered (floating point comparison only)

Math Instructions, without Overflow

CC 1

CC 0




Result = 0



Result < 0



Result > 0

Integer Math Instructions, with Overflow

CC 1

CC 0




Negative range overflow in ADD_I and ADD_DI



Negative range overflow in MUL_I and MUL_DI



Negative range overflow in ADD_I, ADD_DI, SUB_I, and SUB_DI



Division by 0 in DIV_I, DIV_DI, and MOD_DI

Floating Point Math Instructions, with Overflow

CC 1

CC 0




Gradual underflow



Negative range overflow



Positive range overflow



Not a valid floating-point number

Shift and Rotate Instructions

CC 1

CC 0




Bit shifted out = 0



Bit shifted out = 1

Word Logic Instructions

CC 1

CC 0




Result = 0



Result <> 0

BR – Binary Result (bit 8)

The Binary Result transfers the result of the operations
onto the next instruction for reference.  When the BR bit is 1 it enables the output
of the block (ENO) to be TRUE and thus allow other blocks after it to be
processed.  The SAVE, JCB and JNB instructions set the BR bit.

Statement List (STL) Cheat Sheets

If you are a Siemens PLC user then you've more then likely have run into Statement List (STL) programming. STL corresponds to the Instruction List language defined in the IEC 61131-3 specification. The programming is done with very simple mnemonics that can be hard to remember if you don't use it very often.

These cheat sheets provide a quick reference guide for all the instructions and formatting. They are two pages long but if you can print on the front and back then they make for a nice one sheet reference.

STL Listed Alphabetically

STL by AlphabetBest used when trying to interpret an existing program.

Download: PDF (131KB)

STL Listed by Category

STL by Category Best when doing programming.

Download: PDF (140KB)


Connecting IFIX SCADA to Siemens S7 using TCP/IP

Setting up an S7 connection using TCP/IP

The TCP/IP method of communication to the S7-300 and S7-400 PLC's via TCP/IP communication module uses the S7WIN, S7WINSP, S7NT, or S7NTSP protocol.

Software requirements

  • Siemens SIMATIC NET software v6.1 SOFTNET-S7 Industrial Ethernet
  • IFIXSCADA v5.x or above
  • Windows XP + SP1

Hardware requirements

  • Standard network card
  • S7-300 with CPU315-2 DP
  • Siemens power supply PS30/5A
  • Siemens CP343-1 TCP

The hardware modules occupy the following slots in the Siemens PLC:

  1. Siemens power supply
  2. S7-300 CPU 315-2 DP
  3. Ethernet CP343-1 TCP

Example configuration

All wiring should be installed according to Siemens documentation.

Installing the SIMATIC NET software

You must log in as an Administrator to install the SIMATIC NET software. Close all other running applications, including any antivirus software you may be running.

  1. On the SIMATIC NET flash screen, start the installation by clicking Install SIMATIC NET Software.
  2. The PC configuration screen appears. Click Next.
  3. Select the English language option, then click Next. Click Next again.
  4. Click yes to the licensing agreement screen.
  5. Enter your Name and Company on the User Registration screen.
  6. If you already have SIMATIC NET software installed, this will be the drive selected by default. Clear the Run automatic authorization option, and then click next. The Setup: Configuration screen appears.
  7. Select all application options to be installed. (This is necessary if you do not already have STEP7 installed on your machine. If STEP7 v5.2 or higher is already installed, you do not have to select the NCM PC/S7 v5.2 application.) Click Next.
  8. The applications you selected are installed. At the prompt, click OK to restart your system. The system restarts and installs the selected applications. Click Finish to restart your system again.

The SIMATIC NET software is now installed.

Configuring the SIMATIC NET software

This step involves using the Commissioning Wizard to configure the software you installed in the previous step.

Configuring the module

When your system restarts after the software has been installed, your system's hardware configuration is scanned. The Commissioning Wizard appears automatically. (You can also access the Commissioning Wizard at Start/Simatic/SIMATIC NET/Settings/Commissioning Wizard.)

The number of steps required depends on the number of PC Ethernet cards (or modules) detected in your PC. The more modules you operate in the computer, the more steps are required.

  1. Click Next.

    An Ethernet Network Card with with the IP addresses settings shown above was found. This is the network card that will be configured for communication with the Siemens PLC. This is put on index 5.

    Note: The index of the network card can be set with the NCM PC Configuration (hardware configuration). The station index defaults to 5 if you use the Commissioning Wizard.

  2. Select the Use the module for productive operation in configured PC station option, and then click next.
  3. Clear the SIMATIC NET OPC Server in configured PC Station option and select the Configure more applications option. Then click next.
  4. Register the names for your user application: enter VFD1 in the Name text box. This user application is put on index 1. Click Next.

    Note: The name of the application is the VFD name. This comes later in the IFIX Project Editor under Communication | Ports in the Special options text box.
  5. Click Next. This screen appears, confirming you have completed configuring the module:
  6. The configuration is saved and the PC station is reconfigured. Your existing configuration data is overwritten. Click OK to confirm at the prompt.

This completes the module configuration.

Configuring the project with the PC Station Wizard

The next step to configure the project using the PC Station Wizard.

  1. Start the PC Station Wizard.
  2. Choose Create a new project and configuration. A new project is created. Click Next.
  3. Define a new Project name; this example uses IFIXS7. Specify where the copy of the local PC station settings resides, and then click Next.
  4. Select the Edit network and connection configuration option, and then click Finish. NetPro automatically starts, displaying the network configuration.
  5. Click the Application box in the PC station, and then choose Insert | New Connection. The Insert New Connection dialog box appears.
  6. Choose the Unspecified item in the tree. From the Type menu in the Connection area, choose S7 connection. Then click Apply, and then click OK.
  7. In the Properties -S7-Connection dialog box, the local IP Address should be the address of the Ethernet card in the PC. This example uses The partner IP Address should be that of the Ethernet CP343 module in the PLC, in this case The Local ID is the connection identifier of this connection (here it is S7-Connection_1). It will be used later on as the address of the IFIX I/O device. Click Address Details.

    Note: The Local ID S7-Connection_1 is used later in the IFIX Project Editor under Communication | I/O Devices in the I/O Device Address text box. This name is case-sensitive and cannot not contain any spaces.

  8. In the Address Details dialog box, enter the card location of the CPU that the SIMATIC S7 communicates with. Here the card location is 2. Click OK.

    Note: Some power supplies might occupy 2 slots. If so, the card location of the CPU is one higher at 3.

  9. In the NetPro window the new S7-Connection_1 connection appears. Choose Network | Save and Compile. The Save and Compile dialog box appears.
  10. Select the Compile and check everything option, and then click OK.
  11. After completing the save and compile operation, a message appears in the NetPro window. This indicates the warnings and errors present in the configuration. If warnings occur here, then this is to be handled as information only. But if errors occur, the project configuration cannot be loaded. To view errors, choose View |Outputs.
  12. Highlight by clicking on the PC Station (TESTXP). Afterwards the connection table disappears in the message window. From the NetPro menu choose PLC | Download | Selected Stations to transfer the project configuration to the PC. Alternatively, right-click the PC Station and choose Download | Selected Stations.
  13. To confirm the overwrite of configuration data and to proceed with the download, click Yes.
  14. To confirm stopping the Target Module (Network interface Card), click OK.
  15. The configuration should now be successfully loaded. Exit NetPro and click next, and next again to finish the Commissioning Wizard. If you have errors, see for details.

Defining an access point for the application

The next step is to define an access point for the application.

  1. The Configuration Console should appear after terminating the Commissioning Wizard. If it doesn't, open the Configuration Console by selecting START / SIMATIC / Simatic Net / Settings / Configuration Console.
  2. In the Configuration Console dialog box, right-click the Access Point object, and choose New | New access point.

    Note: You can choose any name for the Access point, but it cannot contain spaces and be longer than 32 characters.

  3. In the New access point dialog box, enter your access point name (this example uses IFIXS7). Select the hardware component that will be associated with this access point (TCP/IP -> ASUSTeK/Broadcom 440x in the example).

    Note: The access point name is used later in IFIXSCADA in the Project Editor under Communication | Boards in the Special Options text box. The access point name is case-sensitive.

    After creating the access point the Configuration Console should look like this:
  4. Close the Configuration Console.

This completes the Simatic NET software configuration.

Configuring the S7 driver

The IFIX S7 driver needs three names (settings) from the SIMATIC NET software
configuration. The following points are needed:

SIMATIC NET Configuration
Access point of the application IFIXS7 Boards, Special options
VFD/Application Name VFD1 Ports, Special options Field
Name of the connection (or Local
S7-Connection_1 IODevices, Address Field

Using the Express Wizard

You use the Express Wizard to configure your communications.

  1. In IFIX Explorer, create a new (empty) test project.
  2. In the IFIXSCADA Project Editor, choose Communication | Express Wizard.
  3. In the wizard:
    • Create a new I/O Servers e.g. IOServer.
    • Create a new I/O Device e.g. IODev.
    • Select external as the type of the I/O Device (PLC): Select the Siemens | S7-300 or S7-400| TCPIP using NE2000 network CARD for Windows NT for NT/W2K/XP/2003, or the TCPIP using NE2000 network CARD for Windows 95/98 for 95/98/ME option.
  4. Define the name of the connection. In this example it is S7-Connection_1.

    Note: Do not select the Link I/O Device to an external tag Database option.

This completes this section.

Setting the Access Point

The next step in the process is to set the access point of the application.

  1. Open the Boards dialog box by choosing Communication | Boards.
  2. In the Special Opt text box, enter the access point of the application. This example uses IFIXS7.

Setting the VFD name

The next step is to set the VFD name.

  1. Open the Ports dialog box by choosing Communication | Ports.
  2. In the Special Opt text box enter the VFD Name. In this case VFD1.

Checking the name of the S7 connection

The next step is to check the name of the S7 connection.

  1. Open the I/O Device dialog box by choosing Communication | I/O Devices.
  2. In the Address field enter the name of the connection to the PLC. This example uses S7-Connection_1.

Variable declaration

The next step is to declare the variables.

  1. Open the Tags Form by choosing Tags | Variable Tags.
  2. Create a variable with the following information:
    • Variable Tag Name: TestInteger
    • I/O Device Name: IODev
    • Type: INT
    • Address: DB190,0

Troubleshooting your S7 connection

Question: I receive the following error message when downloading the PC station in the SIMATIC NCM PC manager:

  • "The module "station manager" cannot be contacted. Change the on-line interface."
  • "For On-line connections via the PC internal interface a station name must be assigned in the component configurator. This name must be identical to the name of the PC station, as configured in the STEP7 (or Simatic Net) project."
  • "Online: No connection could be made. The participant does not announce itself."


  1. Check in SIMATIC NCM PC Manager under the Menu option Options | Set PG/PC Interface, whether the point of entrance S7ONLINE is linked with the PC internal (local) interface.
  2. The Station Configuration Editor tells you whether your module is Online. You can start the Station Configuration Editor by double-clicking the icon. This should not be OFFLINE, so to change its mode of operation, click Change Mode. The mode of operation should now change to ONLINE.
  3. Check the station name in the Station Configuration Editor. This must match with the name in SIMATIC NCM PC Manager. You can change the station name in the Station Configuration Editor by clicking Station Name.
  4. Open the Station Configuration Editor and the SIMATIC NCM PC Manager. Check the order and the number of configured components and the indexes that are used. These should match.