Retentivity - Siemens S7-1200 Programming Manualline

3 General Programming

3.5 Retentivity

3.5 Retentivity
In the event of a failure of the power supply, the controller copies the retentive data
with its buffer energy from the controller's work memory to a non-volatile memory.
After restarting the controller, the program processing is resumed with the retentive
data. Depending on the controller, the data volume for retentivity has different
sizes.
Table 3-5: Retentive memory for S7-1200/1500
Controller
CPU 1211C
CPU 1212C
CPU 1214C
CPU 1215C
CPU 1511-1 PN
CPU 1513-1 PN
CPU 1516-3 PN/DP
Table 3-6: Differences of S7-1200 and S7-1500
Retentivity can only be set for bit memory
Advantages
Retentive data maintain their value when the controller goes to STOP and back
to RUN or in the event of a power failure and a restart of the controller.
Properties
For elementary tags of an optimized DB the retentivity can be set separately. Non-
optimized data blocks can only be defined completely retentive or non-retentive.
The retentive data can be deleted with the actions "memory reset" or "Reset to
factory settings" via:
Operating switch on the controller (MRES)
Display of the controller
Online via STEP 7 (TIA Portal)
Recommendation
Avoid the setting "Set in IDB". Always set the retentive data in the function
block and not in the instance data block.
The "Set in IDB" setting increases the processing time of the program
sequence. Always either select "Non-retain" or "Retain" for the interfaces in the
FB.
Programming Guideline for S7-1200/1500
V1.2, Entry ID: 81318674
S7-1200
Usable retentive memory for bit memory,
times, counters, DBs and technology
objects
10 Kbytes
10 Kbytes
10 Kbytes
10 Kbytes
88 Kbytes
88 Kbytes
472 Kbytes
S7-1500
Retentivity can be set for bit memory, times
and counters
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