User Manual

Automation stations
Data storage
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The operating state is stored as a non-volatile variable.
The operating state is mapped as follows to the system status [SysSta]
property of the device object:
Operating mode System status property [SysSta]
STOP (no D-MAP program loaded) DOWNLOAD_REQUIRED
STOP (D-MAP program loaded) NON_OPERATIONAL
RUN (D-MAP program loaded) OPERATIONAL
18.5 Data storage
The following memory types are used in the automation station:
● RAM: The content is lost during a cold start. Read and write access is
possible any time without any special action.
● Battery supported RAM: Operating hours and trend data are preserved
during a cold start if the battery is loaded.
● Flash memory: The content is retained during a cold start. Read access is
possible at any time. Write access is only possible via a special driver and
with restrictions (access time, sequential only).
The data and code of a D-MAP program are saved in the flash memory during
the download process. A copy of the data is always stored in the RAM so that
the D-MAP program can access data efficiently for processing purposes. This
means, that all changes to the program data must be updated both in the RAM
and in the flash memory.
The following figure shows the various sequences:
1. The D-MAP program (code and data blocks) is copied to the flash memory
(1a). A copy of the data blocks is created in the RAM (1b) for later modification
by the D MAP program.
2. When writing data, the data is written to the RAM (2a) and the flash memory
(2b). Read access to the data is via the RAM (2c).
PXM20
XWP
D-MAP
Application
Communication
RAMFlash
Downloading the D-
MAP program
Read/Write via
communication system