Siemens Memory Service Manual download pdf (Page 28)

Memory usage and application examples

3.2 Memory usage for data logging

Structure and Use of the CPU Memory

28 Function Manual, 01/2013, A5E03461664-01

Reference

You can find further information on "Data Logging" instructions in the online help for STEP 7

under "PLC programming > References > References (S7-1200/1500) > Extended

instructions > Recipes and data logging > Data Logging".

3.2.4 Example program for data logging

This example program shows the storing of 3 process values for counter state, temperature,

and pressure in a Data Log.

The example shows the basic function of the instructions for Data Logs. The complete

program logic is not shown.

Note

General use of Data Logs

• Data Logs are automatically opened after execution of the "DataLogCreate" and

"DataLogNewFile" instructions.

• Data Logs are automatically closed when the CPU switches from RUN to STOP and

upon CPU restart.

• Before data can be written to a Data Log with the "DataLogWrite" instruction, the

Data Log must be open.

• No more than ten Data Logs can be open simultaneously, even if there are more than ten

Data Logs.

Tags of the data block

The following figure shows the tags of the "My_Datalog_Vars" data block. These tags are

used by the "Data Logging" instructions "DataLogCreate" and "DataLogNewFile". The

"MyDataLogName" and "MyNEWDataLogName" tags are called in the NAME block

parameter, and give the Data Logs a name. The "MyData" structure is called in the DATA

block parameter and specifies the structure of the csv file. The three MyData tags

temporarily store new values. The tag values at these DB addresses are transferred to a

Data Log using the "DataLogWrite" instruction. The "MyDataLogHeaders" tag is called in the

HEADER block parameter and specifies a header for the Data Log.

Figure 3-4 Declaration table with the data block's tags

1 2 ... 23 24 25 26 27 28 29 30 31 32 33 ... 39 40

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Siemens Memory Service Manual Page 28