Data Protection And Safety; Program Code; Setting Of Parameters (Programming The Dlx) - Baer DLX User Manual

3.2

Data protection and safety

All individual storage cells of the DLX are checked continually:
•
RAM memory:
All storage cells are tested at least once in every 24 hours. The memory
contents are first written to a safe place, then a number of different bit pat-
terns (A5, 5A, 00, FF) are written and read back into each memory cell. Fi-
nally the original memory content is written back. If a defective memory cell
is detected (bit patterns from read and write operations are not identical),
an error message is shown at the display and the error notification relay is
activated. The error message is available for remote data retrieval.
•
Firmware memory:
The content of the firmware memory is tested on an ongoing basis: a
checksum is calculated over the whole memory content. If a difference is
detected between the calculated checksum and the stored checksum, an
error message is shown on the display and the error notification relay is ac-
tivated. The error message is available for remote data retrieval.
•
Data memory:
Data for parameters, spontaneous events, reset events and for each regis-
tration period are stored in physically separate areas (sectors). When data
is written, the correctness of the write cycle is confirmed for each individual
byte of data by an additional read cycle. Additionally a checksum is calcu-
lated for each data set. When data sets are read, another checksum is cal-
culated and compared with the stored checksum. The data set will only be
processed if both checksums are identical.
3.3

Program code

The program code (firmware) is stored in the firmware memory (Flash
memory). Program code can be loaded with a special software application
via the service interface. Therefore no change of EPROM is required for
firmware updates. Loading of a new firmware is only permitted in non-
secured certification mode (in this mode the unit is not certified and the
program protection switch is set to "Disable"). All internal memory will be
cleared and the factory settings (see page 95) will be activated.
3.4

Setting of parameters (Programming the DLX)

Parameter settings in the DLX can be altered via the programming software
DLXPARA or via the keypad (only certain registers), however only after en-
tering a valid password. All modifiable values are differentiated into two
groups: programmable and settable (the list of all registers is contained in
Appendix B). On each change of a parameter of the device, the state of the
program protection switch on the backside of the display will be checked. If
programming is protected (e.g. after certification), then only settable values
can be altered. Modification of programmable values is only possible after
removing the certification seal. If relevant regulations exist, the device must
then be re-certified afterwards. Once the program protection switch is de-
activated, all variable values can be modified.
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