Siemens SINUMERIK MC Commissioning Manual page 91

Data block
In order to process tags of the standard user program in the safety program, you can read tags
from data blocks of the standard user program in the safety program. However, a read tag must
not be written in the safety program itself.
Note
It is not possible to access static local data in single/multi-instances of the FBs of the standard
user program.
Process image of the inputs
You can read the process image of the inputs (PII) of standard I/O in the safety program. The
PII must not be written in the safety program.
Examples: Programming validity checks
● Check non-safety relevant tags from the standard user program using operations to
compare whether a permissible upper/lower limit is violated (exceeded/fallen below). You
can then influence your safety function with the result of the comparison.
● With non-safe variables from the standard user program, e.g. using instructions "S: set
output", "R: reset output" or "SR: set/reset flip-flop" only allow the motor to be switched off,
but do NOT allow it to be switched on.
● For switch-on sequences, use the AND logic operation instruction, for example, to logically
combine unsafe tags from the standard user program with switch-on conditions that you
derive from failsafe tags.
If you want to process standard tags in the safety program, please bear in mind that there is not
a sufficiently simple method of checking validity for all unsafe tags.
Reading tags from the standard user program that can change during the runtime of an F‑runtime group
If, in the safety program, you wish to read variables from the standard user program (bit
memories, variables of a standard DB or PII of the standard I/O), which - during the runtime of
the F-runtime group in which they are being read - can be changed by the standard user
program or an HMI system – for example, because your standard user program is processed
by a higher priority cyclic interrupt – then you must use separate bit memories or variables of
a standard DB.
You must create the standard DB with the same priority as the F-OB. You must call the standard
OB with a phase offset with respect to the F-OB, and write to the variables in this.
We recommend that you select the phase offset so that the standard OB is processed
immediately before the F-OB.
You are then permitted to access only this bit memory or these tags of a standard DB in the
safety program.
Safety Integrated (with SINAMICS S120)
Commissioning Manual, 02/2020, A5E46305916B AB
3.15 Data exchange between the standard user program and safety program
Safety program of the F-PLC
91