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Entry type: FAQ Entry ID: 8686578, Entry date: 02/17/2009
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How can you set up the online connection again between the PG and the CPU?

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Instructions:
In some cases it can happen that an online connection cannot be set up between the PG and the module and an error message is displayed. Most causes can be determined through the notes in the Online Help which you reach by clicking on "Help". The table below describes some measures and remedies that can be applied when communication or an online connection is not possible between the programming device and the CPU. The most common reasons for loss of the online connection are as follows:

  1. Incorrectly configured module in the HW Config
  2. Incorrectly configured address
  3. Incorrectly set PG/PC interface
  4. Baud rate doesn't match the network baud rate
  5. Not enough memory on the hard disk for the swap file
  6. Incorrectly set PROFIBUS DP interface
  7. Incorrectly set MPI interface
  8. Differences in the program between online and offline
  9. Permitted cycle time increase set too low
  10. Incorrectly set bus profile
  11. More than one Ethernet interface in the same IP subnetwork
No. Remedies for setting up the online connection
1 Incorrectly configured module in the HW Config
Check whether the modules slotted in the rack (CPU, CPs) have the correct hardware configuration. The CPU and CP types must match the configuration. If you have configured an incorrect module, the system block loading procedure might be aborted and you get an error message like:
  • Downloading (13:4589)
    The system data cannot be downloaded to module ... of station ... .
    "SDB 200 cannot be downloaded",
    or "(D225) The DP system data block has invalid parameters".

Remedy:
In the Hardware Configuration you configure the modules with the correct MLFB number (e.g. 6ES7315-2AF03-0AB0 for a CPU 315-2DP). Save and compile the hardware configuration and repeat the downloading procedure.

2 Incorrectly configured address
If you have configured an MPI or PROFIBUS address in the Hardware Configuration which doesn't correspond to the node address (CPU), you get the following error message:
  • Downloading (33:16656)
    "Online: No connection established. No response from connection partner."

Execute the function "PLC > Show Accessible Nodes". In the "Accessible Nodes" window are the addresses for MPI and PROFIBUS under which the module can be accessed. If, for example, the address MPI=2 is shown in the window, then the MPI address 2 must also be set for the CPU in the Hardware Configuration.


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Remedy:
If necessary, change the MPI address for the CPU in the HW Config. Save and compile and then reload the HW Config into the module.

More detailed information on the error message mentioned above is available in the Online Help. For this click on the "Help" button in the error message and follow the description for clearing the fault, e.g.

  • check the plug-in cables and the connection to the network.
  • Check the available voltage.
3 Incorrectly set PG/PC interface
If the parameters of the PG/PC interface do not match the online connection or the interface has yet been installed, then you get the following
error message:
  • Downloading (288:47)
    "Module ... cannot be reached via the online interface set".

Open the PG/PC interface via the menu "Tools > Set PG/PC interface..." and in the "Interface Parameter Assignment Used:" window, check whether you have set the correct interface for your online connection.


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If the required interface is not available, click on the "Select" button and install the relevant driver in the "Install/Remove Interfaces" dialog. In this case mark the required interface in the "Selection:" window on the left and click on the "Install -->" button. After installation the interface is shown in the "Installed:" window on the right.


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Then close the dialog and select the interface in the "Interface Parameter Assignment Used:" dialog. Close the PG/PC interface with OK.

4 Baud rate doesn't match the network baud rate
If you have set a baud rate for the module in the HW Config that doesn't match the network baud rate, you get the following error message:
  • Downloading to module (33:17075)
    "Online: The local MPI address of the PG/PC is longer than the maximum size permitted for node addresses or an incorrect baud rate or incorrect interrupt has been set".

Open the PG/PC interface via the menu command "Tools > Set PG/PC interface..." and click on the "Diagnostics..." button. By clicking on the "Test" button you receive the PROFIBUS/MPI network diagnostics. Fig. 04 shows an example of when the baud rate or interrupt doesn't match (error 0x0313).


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In the "Hardware" tab you can use the "Test" button to diagnose which resources are used by the module. Before running the diagnostics refer to the now in the Online Help (under "Help" and close all other applications and save your data before the test.


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Close the dialog with OK and in the "Set PG/PC interface" dialog click on the "Properties" button. In the "Properties" dialog you select the correct transmission rate for the network.


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5 Not enough memory on the hard disk for the swap file
Check the virtual main memory and refer to the relevant notes in the readme file (section 3.2 Memory Requirements). We recommend setting 1000 MB to 1500 MB. More information on setting the virtual main memory in the various Windows operating systems is also available in Entry ID: 20440472 (Notes on optimizing performance).
6 Incorrectly set PROFIBUS DP interface
You want to set up an online connection via the PROFIBUS DP interface of a CPU 317-2-PN/DP, for example, and there is also PROFIBUS DP interface configured in the Hardware Configuration. The online connection setup will be aborted in the interface parameters are not correct or the PROFIBUS address in the HW Config is incorrect. The following error messages are displayed:
  • "Download to PG (13:4337): Connection to module ... in station ... could not be set up"
    (in the hardware configuration), or
  • "Monitoring (288:47): Module ... cannot be reached via the online interface set"
    (in the LAD/STL/FBD editor)

Remedy:
Open the PG/PC interface via the menu command "Tools > Set PG/PC interface..." and select the correct access point for the interface you are using e.g. CP5512(PROFIBUS). We recommend that you select an interface with automatic recognition of the bus parameters, e.g. CP5512(Auto). Via this access route you can connect the PG to MPI or PROFIBUS without having to set the bus parameters. Please refer here also to the notes in the Online Help under "Setting the PG/PC Interface".


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Via "PLC > Show Accessible Nodes" you get a display of the accessible address (e.g. "PROFIBUS = 2"). You must set the address for the CPU module in the Hardware Configuration in order to reach the CPU online.

7 Incorrectly set MPI interface
If the MPI interface is not set in the PG/PC interface, the online connection setup is aborted in the LAD/STL/FBD editor and in the Hardware Configuration accompanied by the error messages described in Point 6. Most likely the interface for the PROFIBUS is still configured in the PG/PC interface for the MPI connection configured.

Remedy:
In the PG/PC interface, select the access point for MPI (e.g. CP5512(MPI)) for the interface you are using, or the interface with automatic recognition of bus parameters (e.g. CP5512(Auto)). Pay attention here too, as described in Points 2 and 6, that you have the correct MPI address that you can determine via the menu command "Show Accessible Nodes".

8 Differences in the program between online and offline
If you can no longer activate the "Monitoring" function during the program test in online mode, then please check whether there are differences in the program between the online representation and offline representation. In this case the button with the spectacles used to select this function is inactive or grayed out.

If you make changes in offline mode, then you must first load your program into the CPU before you can activate the "Monitoring" function.

9 Permitted cycle time increase set too low
In the processing operation only the cycle time is required for processing the program, but for testing the program with the variables table (VAT) you need an additional increase in the cycle time. If you just have short program and in comparison a large variables table with a short cycle time increase, then when monitoring and controlling the variables table the program aborts with the error message "(D0AA) Time limit exceeded in processing operation".


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Remedy:
In the Hardware Configuration you open the object properties of the CPU and select the "Protection" tab. You have two options here:

  1. Select Test Mode for testing.
  2. Select a higher permitted increase in cycle time for the Process Mode.

Acknowledge all the dialogs with OK and save and compile the hardware configuration.


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Load the hardware configuration into the CPU and then you can test the program using the variables table.

10 Incorrectly set bus profile
If the bus profile setting in the PG/PC interface is different to the bus profile configuration in the Hardware Configuration, setup of the online connection is aborted with the following error message:
  • "Monitoring (33:16945), Online: the bus is defective" or
  • "Show accessible nodes (33:16914), Online: The station is not online".

For your PROFIBUS DP interface, check whether bus profile of your configured CPU matches the setting in the PG/PC interface. In the Hardware Configuration, open the properties of the DP interface of the configured CPU and select the dialog "Properties - PROFIBUS" via

  • "Tab: General > Properties... > Tab: Parameters > Properties > Tab: Network Settings".

The configuration for the profile (e.g. "DP" or "Standard") must also be set in the PG/PC interface.


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In the SIMATIC Manager, open the PG/PC interface and click on the "Properties" button. Select the relevant profile (e.g. "DP" or "Standard") for your PROFIBUS DP interface.


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11 More than one Ethernet interface in the same IP subnetwork
The error message (33:16656) described under point 2 can also be displayed if for a TCP/IP connection you have set up more than one Ethernet interface in the same IP subnetwork. In order to set up the selected Ethernet interface for an online connection, you must first disable the unused Ethernet interface.

Remedy:
In Windows XP, you open the dialog "Start > Settings -> Network connections" and right-click on the unused Ethernet. Then click on the "Disable" button in the pop-up menu.

Note:
More information on setting up the online connection is available in our FAQs:

  • "How do Diagnostics and Remedy work in in STEP 7 when an online connection with the CP5511 is not possible?"
    Entry ID: 11492532
  • "Why can't you set up an online connection any more after installing STEP 7 version V5.4 with a PC/TS adapter?"
    Entry ID: 23933965
  • "Is there a check list for implementing a PC adapter?"
    Entry ID: 10420976

Keywords:
Connection setup, Communication setup, Program development

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