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Tuesday, March 3, 2009

How can you load projects to a memory card and back again to a PG/PC?

Instructions:
From STEP 7 V5.1, you can save all the data for a project on a memory card using the "Store on memory card..." function and then retrieve it again, to use later on for example, with "Retrieve from memory card...". To do this, you can insert the memory card into a CPU or into the memory card programming device on a PG or PC. However, project data storage and retrieval on a memory card is only available for modules which support this function. At present, they are S7-400 CPUs and S7-300 CPUs with MMC memory cards".

Before being saved to memory card the project data is compressed and decompressed when retrieved. Here you must choose the size of the memory card that is able to store not only the project data, but also the user data. The size of the project data to be saved corresponds to the size of the project's archive file. If the capacity of the memory card is not sufficient, you are informed of this by a message.

The table below describes the procedure for a number of applications.

No. Procedure:
1 Memory card is located in the CPU
If the memory card is located in a module which supports this function, only the complete content (user program and project data) can be transferred when applying the two "Store on memory card..." and "Retrieve from memory card..." functions for technical reasons.

In the project window of the SIMATIC Manager you select a project level that is uniquely assigned to the CPU (e.g. CPU, program, sources or blocks) and select the menu command "PLC > Save to Memory Card..." or "PLC > Retrieve from Memory Card...". Now the complete project data is written to the memory card or retrieved from it.


Fig. 01

2 Project data not available in the programming device (PG/PC)
If the project data is not available in the programming device (PG/PC), then the source CPU can be selected in the "Accessible Nodes" dialog.
  • Open the "Accessible Nodes" dialog via the menu command "PLC > Show Accessible Nodes" and select the desired connection/CPU with the project data on the memory card.
  • Now select the menu command "Retrieve from Memory Card...".
3 Memory card in the memory card programming device
If the memory card is in the memory card programming device of a PG or PC, then proceed as follows:
  • Open the S7 memory card window with the menu command "File > S7 Memory Card > Open".
  • Select the menu command "PLC > Save to Memory Card..." or "PLC > Retrieve from Memory Card..." (see Fig. 01).

In the dialog that then opens you can select the source project or target project respectively.


Fig. 02

4 "Download User Program to Memory Card" function
The "Download User Program to Memory Card" function downloads a user program to the memory card of a CPU. Under the following conditions you can also save the STEP 7 project to the memory card:
  • The CPU must have a slot for a memory card.
  • The CPU must support this function (e.g. CPU416).
  • A memory card must be slotted.

This function can only be executed in the STOP mode of the CPU. During the transfer, all the blocks in the load memory of the CPU and on the memory card are deleted. Proceed as follows:

  1. Slot the memory card into the CPU.
  2. In the "Offline" view, mark the block folder whose blocks are to be copied to the memory card.
  3. Select the menu command "PLC > Download User Program to Memory Card".


Fig. 03

More information on the memory card is also available in the STEP 7 Online Help.

5 "Upload Station to PG" function
With the menu command "PLC > Upload Station to PC..." you can read back the complete project data from the CPU to a PG/PC. For this, however, a new station is created in the current project and the configuration and blocks copied into the new station. In the blocks in the uploaded station there are no symbolic designations like temporary tags, markers, formal parameters and all comments.

Therefore it is only useful to use this function for service when there is no offline project available, for example. More information on the restrictions when using the above-mentioned function is available in the STEP 7 Online Help.

6 "Upload to PG" function
With the menu command "PLC > Upload to PG" you can copy blocks from the online block container to the offline block container on the PG. In contrast to the "Upload Station to PG" function, this function permits you to retrieve blocks from the CPU to the data management of the original project on the PG/PC. Similarly you can copy blocks from the online block container to the offline block container.

Note:
A user program contains all the functions required for processing the specific solution for the automation task. The user program's tasks are:

  • To define the requirements for rebooting and restarting the CPU.

  • To process the process data (link binary signals and define them for output, read, evaluate and output analog values).

  • To respond to alarms and process faults in the normal course of the program.

A project is the entirety of all the data and programs of an automation solution and is at the top of the object hierarchy. The project contains the following objects:

  • S7 hardware setup (hardware configuration) of the S7-300/400 station.

  • Programmable modules CPUxx, CPxx and FMxx.

  • S7 program (folder for the software).

  • Source folder (with the source programs) and the block folder (SDBs, DBs, UDTs, FBs, FCs and OBs).

Keywords:
Data backup, Project backup, Read-back, MMC

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