Siemens SIMATIC S7-300 Manual page 214

Description of Functions
Retentive storage Please note the following when using the function "Write parameters with
of parameter data
retentive storage" (byte 4, job type 4):
Retentive writing must only occur on demand (not cyclically)!
Retentive data are stored on FEPROM (maintenance–free, no battery re-
quired). This memory has a physical limit for the possible number of delete/
reprogram cycles: minimum 10
lete/reprogram cycles can be multiplied, from the user's viewpoint, by
providing a larger retentive memory capacity (much larger than the parame-
ter data memory) and organizing the memory accordingly.
Number of delete/re-
program cycles
Block sizes:
DB Machine data
DB Increments
DB Tool offset data
DB Traversing programs
Example:
Assuming a service life of 10 years and 24–hour operation, a typical limit =
10
MD
Traversing pro-
grams (20 blocks)
Note
SDB
parameter data which were valid at the time of start–up. If data/parameters
are modified during operation and stored retentively on the FM, these data
are not contained in SDB
module is replaced, and should be traceable in the user program.
9-38
=
Block size (in bytes), in which param-
eter data are modified
6
.
Parameterization DB size
data
250 bytes 256 10
510 bytes 125.49 10
1 000 (system data block, created for module replacement), contains
1 000. These modifications are lost when the
5 6
, typically 10 . The possible number of de-
6
64 000 10 (typical)
approx. 250 bytes
approx. 460 bytes
approx. 310 bytes
110 + (20 x no. of traversing blocks) bytes
Number of possible de- Number of possible de-
lete/reprogram cycles lete/reprogram cycles
6
49
6
24
FM 354 Servo Drive Positioning Module
per minute