Measured Value Log Files - Siemens Simatic S7-300 Technical Data Manual

4.2.6

Measured value log files

Introduction
Measured values are generated when the CPU executes the user program. These values
are to be logged and analyzed.
Processing sequence
Acquisition of measured values:
• The CPU writes all measured values to a DB (for alternating backup mode in several
Measured value logging:
• Before the data volume can exceed work memory capacity, you should call
Loading memory
Measured values 1
Measured values 2
Measured values n
• You can call SFC 82 "CREA_DBL" in the user program to generate new (additional) static
Reference
For detailed information on SFC 82, refer to the
and Standard Functions
Note
SFC 82 is terminated and an error message is generated if a DB already exists under the
same number in load memory and/or RAM.
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
DBs) which is located in RAM.
SFC 84 "WRIT_DBL" in the user program to swap measured values from the DB to load
memory. The figure below shows how to handle measured value log files:
(MMC)
:
DBs in load memory which do not require RAM space.
Reference Manual, or directly to the STEP 7 Online Help.
SFC 82 CREA_DBL
SFC 84 WRIT_DBL
System Software for S7-300/400, System
Memory concept
4.2 Memory functions
Working memory
(CPU)
Current measured
values
4-17