Specifications

3 General Programming

3.5 Retentivity

Programming Guideline for S7-1200/1500

V1.2, Entry ID: 81318674

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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

Usable retentive memory for bit memory,

times, counters, DBs and technology

objects

CPU 1211C 10 Kbytes

CPU 1212C 10 Kbytes

CPU 1214C 10 Kbytes

CPU 1215C 10 Kbytes

CPU 1511-1 PN 88 Kbytes

CPU 1513-1 PN 88 Kbytes

CPU 1516-3 PN/DP 472 Kbytes

Table 3-6: Differences of S7-1200 and S7-1500

S7-1200 S7-1500

Retentivity can only be set for bit memory

Retentivity can be set for bit memory, times

and counters

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.