Siemens SIMATIC S7-300 Series Reference Manual page 36

CPUs
Different Features of Forcing S7-300
Please note the different features of forcing in the different CPUs:
The variables of a user program with
fixed preset values (force values)
cannot be changed or overwritten by
the user program.
It is not permissible to force peripheral
or process image areas lying in the
range of consistent user data.
The following can be variables:
Inputs/outputs
Peripheral I/Os
Memory markers
You can force up to 256 variables.
1-20
CPU 318-2
PLC S7-300, CPU Specifications CPU 312 IFM to CPU 318-2 DP
CPU 312IFM to 316-2DP
The variables of a user program with
fixed preset values (force values) can
be changed or overwritten in the user
program.
(See Figure 1-4 on page 1-21)
The following can be variables:
Inputs/Outputs
You can force up to 10 variables.
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