Siemens S7-300 Installation And Operating Manual page 338

Glossary
Nonequivalent sensor
A nonequivalent → sensor is a two-way switch that is connected (via two channels) to two
inputs of an → F-I/O in → fail-safe systems (for → 1oo2 evaluation of sensor signals).
P switch
→ M switch
Parameter assignment
Assigning parameters using PROFIBUS DP: Transfer of slave parameters from the DP
master to the DP slave.
Parameter assignment of modules/submodules: Assigning the behavior of
modules/submodules with the
Passivation
An → F-I/O sets the corresponding channel or all channels to → safe state when it detects a
fault, that is, it passivates its channels. The F-I/O reports the fault to the → F-CPU.
If F-I/O inputs are passivated the → F-system returns fail-safe values to the → safety program
instead of the process values set at the fail-safe inputs.
If F-I/O outputs are passivated the → F-system returns fail-safe values to the fail-safe outputs
("0") instead of the output values returned by the → safety program.
PG
Programming device Compact PC designed for use in industry. A programming device is
fully equipped for programming SIMATIC automation systems.
Process image
The process image is a part of CPU system memory. The signal states of the input modules
are transferred to the process image of inputs at the start of cyclic program execution. The
process image of the outputs is transferred to the output modules as a signal state at the end
of the cyclic program execution.
Process safety time
The process safety represents the interval during which a process may be allowed to
continue without intervention, without developing any risk to life and limb of operating
personnel or damage to the environment.
Any type of F-system process control is tolerated within the process safety time, that is, the
process can be controlled incorrectly or not at all. The process safety time of a process
depends on the process type and must be determined individually.
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STEP 7
configuration software.
Installation and Operating Manual, 01/2010, A5E00085586-10
Fail-safe signal modules