Siemens SIMATIC Operating Instructions Manual page 168

Glossary
Process Image
The process image is a component of the system memory of the CPU. At the beginning of
the cyclic program, the signal states of the inputs are transferred to the process input image.
At the end of the cyclic program, the process output image is transferred as a signal state to
the outputs.
Process Safety Time
The process safety time of a process is the time interval during which the process can be left
on its own without risk to life and limb of the operating personnel or damage to the
environment.
Within the process safety time, any type of F-system process control is tolerated. That is,
during this time, the -> F-system can control its process incorrectly or it can even exercise no
control at all. The process safety time depends on the process type and must be determined
on a case-by-case basis.
PROFIBUS
PROcess FIeld BUS, process and fieldbus standard defined in IEC 61784-
1:2002 Ed1 CP 3/1. This standard specifies functional, electrical and mechanical properties
for a bit-serial fieldbus system.
PROFIBUS is available with the following protocols: DP (= distributed I/O), FMS (= fieldbus
message specification), PA (= process automation), or TF (= technological functions).
PROFINET IO
PROFINET IO is the PROFINET communication concept for implementing modular,
distributed applications.
PROFINET IO enables the creation of automation solutions using the familiar, proven
methods of PROFIBUS.
PROFINET IO is implemented based on both the PROFINET standard for automation
devices and the
This means that you have the same application view in
are configuring PROFINET or PROFIBUS devices. Creation of your user program is similar
for PROFINET IO and PROFIBUS DP, provided you use the expanded blocks and system
status lists for PROFINET IO.
PROFINET IO Controller
A PROFINET IO controller is a device that is addressed via the connected IO device. That is,
the IO controller exchanges input and output signals with assigned field devices. The IO
controller is often the controller in which the automation program runs.
PROFINET IO Device
A PROFINET IO device is a distributed field device that is assigned to one of the IO
controllers (e.g., remote IO, valve terminals, frequency converters, switches).
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STEP 7
engineering tool.
STEP 7
, regardless of whether you
ET 200pro Distributed I/O System - Fail-Safe Modules
Operating Instructions, 05/2007, A5E00394073-02