Siemens Industry Online Support
Siemens AG
Entry type: FAQ Entry ID: 109758852, Entry date: 07/25/2018

Important settings when using Motion Control functions with an Open or Software Controller

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If you are using a software controller on a SIMATIC IPC without NVRAM, it might happen that if the IPC is not shut down properly, there is data loss, the absolute value encoder adjustment, for example.

If you use SIMATIC IPC without the optional NVRAM in conjunction with the software controller, if the IPC is not shut down properly there might be data loss, encoder data, for example, when implementing Motion Control functions and absolute value encoders, for example. It is therefore recommended to use an appropriate UPS or consider an NVRAM when ordering the IPC.

In order to avoid data loss with the SIMATIC IPCs make sure that

  • either the IPC is always completely shut down (Retentive data memory setting: "PC mass storage") or

  • the storage location of the retentive data is set to "NVRAM of the PC system" and the device has an NVRAM.

You can order SIMATIC IPCs with or without NVRAM. However, you cannot retrofit this NVRAM storage.
The default setting for the storage location of the retentive data with SIMATIC IPCs is ""PC mass storage" regardless of whether or not there is an NVRAM. The user has to change the setting of the storage location.

In the case of Open Controllers there is always an NVRAM and the default setting is "NVRAM of the PC system".

Set storage location for retentive data

When shut down or in the case of a power failure, the CPU provides the option of saving the data retentive in the mass storage of the PC or in the integrated NVRAM. You set the type of data storage in the Properties of the CPU in STEP 7.

Data loss when changing the storage type
If you change the storage type the current retentive data and the contents of the diagnostics buffer are deleted.

Proceed as follows to configure the storage type:

  1. Select the software controller.

  2. In the inspector window select the "General" tab and under "Advanced configuration" you choose "Retentive memory".
  • Enable the option "PC mass storage" to save the retentive data in the mass storage of your PC.
  • Enable the option "NVRAM of the PC system" to save the retentive data in the integrated NVRAM of your PC.

3. In order to then change the type of data storage in STEP 7 you reload the project into the target device.

If you change the storage location for retentive data, you have to load the complete PC system.
The PC system is booted during the loading procedure and the previous retentive data is deleted.

This FAQ response is valid for the following SIMATIC IPC types:

  • Rack PC 
    • IPC647D (RACK PC)
    • IPC847D (RACK PC)
  • Box PC 
    • IPC627D (BOX PC)
    • IPC827D (BOX PC)
  • Panel PC 
    • IPC677D
  • Open Controller 
    • CPU1515SP PC2 Standard / T / TF

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