Data Logs - Siemens S7-1200 System Manual

Extended instructions
8.7 Recipes and Data logs
Network 5 READ_DBL copies the start values from one recipe "Recipe_DB".Products[1] (in
CPU load memory) to the Active_Recipe DB current values (in CPU work memory). After
READ_DBL execution, your program logic can access the recipe component values by
addressing locations in the Active_Recipe DB. For example, the symbolic addresses (
"Active_Recipe".productname) and ("Active_Recipe.water) provide your program logic with
the current recipe name and quantity of water.
Network 6 During run time, An HMI device could modify a component value stored in the
Active_Recipe DB. Improved recipe data can be stored by executing WRIT_DBL. In the
example, all Recipe_DB start values for the single recipe "Recipe_DB".Products[1] are
overwritten by the current values from the "Active_Recipe" DB.
8.7.2

Data logs

Your control program can use the Data log instructions to store run-time data values in
persistent log files. The data log files are stored in flash memory (CPU or memory card). Log
file data is stored in standard CSV (Comma Separated Value) format. The data records are
organized as a circular log file of a pre-determined size.
The Data log instructions are used in your program to create, open, write a record, and close
the log files. You decide which program values will be logged by creating a data buffer that
defines a single log record. Your data buffer is used as temporary storage for a new log
record. New current values must be programmatically moved into the buffer during run-time.
When all of the current data values are updated, you can execute the DataLogWrite
instruction to transfer data from the buffer to a data log record.
You can open, edit, save, rename, and delete data log files from the File Browser page of
the Web Server. You must have read privileges to view the file browser and you must have
modify privileges to edit, delete, or rename data log files.
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S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG