Supported operand areas
The system memory of an F-CPU is divided into the same operand areas as the system
memory of a standard CPU. You can access the operand areas listed in the table below from
within the safety program.
Table 3-1 Supported operand areas
Operand area Description
Process image of the inputs
● Of F-I/O
Only read-only access to input channels of F-I/O is possible.
Transfer to IN_OUT parameters of an F-FB or F-FC is therefore not valid
either.
The process image of the inputs of F-I/O is updated prior to the start of
the main safety block.
● Of standard I/O
Input channels of standard I/O can only be accessed read-only.
Transfer to IN_OUT parameters of an F-FB or F-FC is therefore not valid
either.
In addition, a process-specific validity check is required.
See the
STEP 7 help
for the update times of the process image of the
inputs of standard I/O.
Process image of the outputs
● Of F-I/O
Only write-only access to output channels of F-I/O is possible.
Transfer to IN_OUT parameters of an F-FB or F-FC is therefore not valid
either.
In the safety program, the values for the outputs of the F-I/O are calcu‐
lated and stored in the process image of the outputs.
The process image of the outputs for F-I/O is updated after the end of
the main safety block.
● Of standard I/O
Output channels of standard I/O are write-only channels.
Transfer to IN_OUT parameters of an F-FB or F-FC is therefore not valid
either.
In the safety program, the values for the outputs of the standard I/O are
also calculated and stored in the process image of the outputs, if nee‐
ded.
See the
STEP 7 help
for the update times of the process image of the
outputs of standard I/O.
Bit memory This area is used for data exchange with the standard user program.
In addition, read access requires a process-specific validity check.
A particular element of the bit memory can be either read- or write-ac‐
cessed in the safety program.
Transfer to IN_OUT parameters of an F-FB or F-FC is therefore not valid
either.
Note that it is only permitted to use bit memory for connecting the stand‐
ard user program and the safety program; it must not be used as a buffer
for F-data
.
Data blocks
Safety program of the F-PLC
3.5 Restrictions in the programming languages FBD/LAD
Safety Integrated (with SINAMICS S120)
Commissioning Manual, 02/2020, A5E46305916B AB 65
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