DRAM file system (SW 2.2 and higher)
Siemens AG, 2003. All rights reserved
SINUMERIK 840Di Manual (HBI) – 06.03 Edition
For historical reasons, the passive file system of the NCK in which the user
data, such as parts programs, user cycles, etc. are located is in the SRAM area
of the NCK.
The SINUMERIK 840Di has retained this system architecture, among other rea-
sons, because of the increased data security:
– Data retention also in case of a power fail event
– Protection from overwriting because no access to this memory area is
possible by Windows NT applications.
The function DRAM file system permits relocation of data areas are in the
SRAM area of the NCK by default into the DRAM file system by activating a
machine data. The memory that that releases in the SRAM can be used, for
example, for more or larger parts programs.
Because when you switch off the NCK, the memory content of the DRAM is lost,
the DRAM file system requires a retentive background memory. The DRAM file
system is reloaded from this retentive background memory every time the NCK
is booted. On the SINUMERIK 840Di, the hard disk of the PCU is used as the
To ensure data consistency, not only the entire SRAM but also the retentive
background memory of the DRAM file system is cleared with the function "Clear
NC data", for example, before restart-up of the NCK.
The maximum size of the DRAM file system in Kbytes can be set in the ma-
MD18351: MM_DRAM_FILE_SIZE (size of DRAM file system).
To ensure system compatibility with the SINUMERIK 840D, the DRAM file sys-
tem of the SINUMERIK 840Di requires configuration of a flash file system (FFS).
The size of the FFS in Kbytes can be set in the machine data:
MD18332: MM_FLASH_FILE_SYSTEM_MEM_SIZE (size of the FFS)
The size of the DRAM file system and the FFS should currently be set to be
equal, but in any case, the FFS must be greater than or equal to the DRAM file
The max. size per file system is 4MB.
In SW 2.2 and higher, Siemens, machine manufacturer and user cycles can be
swapped to the DRAM file system. This swapping has no effect on the use of
10 NC Start-Up with HMI Advanced
10.4 Memory configuration