Mdt User Data Area; Mdt System Data Area - Bosch Rexroth ID 40 Manual

4.2.1

MDT user data area

The user data area contains all production-related and product-related data.
The following applies for this area:
• The user has direct write and read access
• The data is organized in a byte array with 16-bit index, the MDT address. The MDT
address is presented in this manual in hexadecimal format. The first byte in the
user data area has the MDT address 0x0000.
• The smallest readable/writable data volume is 1 byte.
• The user data area in the MDT2K is 1,904 bytes, in the MDT8K 7,664 bytes, and
in the MDT32K 30,800 bytes. The remaining memory is reserved for registers and
system data.
• The contents of the data are transparent, i.e., not interpreted by the SLK. This
means the user can generate any data structure on the MDT.
4.2.2

MDT system data area

Checksums are stored in this area and the user does not have access.
All data stored on the MDT is secured with checksums.
The user data is secured in blocks, i.e., each data block is assigned a checksum. The
block size is 16 bytes. The advantage of this is that the checksums do not take up
much memory and memory errors can be localized precisely. Data not located in a
block flagged with an error can continue to be used in the application.
The 16-byte blocks always begin on an address divisible by 16.
For example, the first three 16-byte blocks in the MDT memory:
Table 6: Segmentation of the user data area
0x002F
0x0020
0x001F
0x0010
0x000F
0x0000
The checksums are verified on a 16-byte block with each read or write access. If an
error is detected, attempting to read this data results in an error sent to the SLK.
The data itself flagged with the error is also returned during read access. This allows
the user to assess the plausibility of the contents of the data.
An error bit is also entered in the MDT status register. This causes the status display
of the MDT to show red.
MDT memory structure
User data
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Checksum 3
Checksum 2
Checksum 1