Siemens SIMATIC S7-400 Reference Manual page 449

Noise suppression
Parameter in STEP 7 for analog input modules. The frequency of the alternating voltage power
supply can interfere with the measured value, in particular when measuring small voltage
ranges and with thermoelements. With this parameter, the user specifies the predominant
power supply frequency in the system.
Non-isolated
With non-floating input/output modules, the reference potentials of the control and load circuits
are electrically interconnected.
Operating state
The automation systems of SIMATIC S7 recognize the following operating modes or simply
modes: STOP, → STARTUP, RUN and HOLD.
Operational limit
The operational limit is the measurement or output error of the analog module throughout the
entire temperature range related to the nominal range of the analog module.
Parameters
1. Variables of a → logic block
2. Variable for setting the properties of a module (one or more per module). When shipped,
every module has practical basic parameter settings that the user can modify in STEP 7.
Point-to-point link
On a point-to-point link, only two nodes are physically linked to each other. This type of
communications link is used when the use of a communication network is not practical or when
different types of nodes need to be connected (for example, PLC with process computer).
Priority class
The S7 CPU operating system provides up to 28 priority classes (= program execution levels"),
for example for cyclic program execution, hardware interrupt-controlled program execution.
Each priority class is assigned to → organization blocks in which the user can program a
reaction. The OBs have different default priorities and if the OBs are called at the same time,
the priority decides which executes first and which can interrupt another. The default priorities
can be modified by the user.
Process image
The signal states of the digital input and output modules are entered in a process image on
the CPU.
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
Glossary
449