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:
Downloading the D-MAP program
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.
Read/Write via communication system
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).
Processing the D-MAP program
3. The D-MAP program code is read from the flash memory (3a). The program data is modified in the RAM (3b). Non-volatile process variables (e.g., adaptive control parameters, hours run, etc.) are written by the function blocks into the flash memory (3c) at regular intervals (once per day) or saved in the battery supported RAM.
Starting the automation station
4. At each restart of the automation station, a copy of the data (data blocks) is created in the RAM (4) from the flash memory (including all communication and D-MAP changes).