Glossary
S7-300, CPU 31xC and CPU 31x: Installation
Glossary-12 Operating Instructions, Edition 08/2004, A5E00105492-05
Nesting depth
A block can be called from another by means of a block call. Nesting depth is referred to as
the number of simultaneously called code blocks.
Network
A network consists of one or more interconnected subnets with any number of nodes.
Several networks can exist alongside each other.
A network is a larger communication system that allows data exchange between a large
number of nodes.
All the subnets together form a network.
Node
See PROFIBUS node
Within the context of PROFINET, "node" is the generic term for:
• Automation systems
• Field devices (for example, PLC, PC, hydraulic devices, pneumatic devices)
• Active network components (for example, distributed I/O, valve blocks, drives)
The main characteristics of a node is its integration into PROFINET communication by
means of Ethernet or PROFIBUS.
The following device types are distinguished based on their attachment to the bus:
• PROFINET nodes
• PROFIBUS nodes
Non-isolated
The reference potential of the control and on-load power circuits of non-isolated I/O modules
is electrically interconnected.
OB
See Organization blocks
OB priority
The CPU operating system distinguishes between different priority classes, for example,
cyclic program execution, process interrupt controlled program processing. Each priority
class is assigned organization blocks (OBs) in which the S7 user can program a response.
The OBs are assigned different default priority classes. These determine the order in which
OBs are executed or interrupt each other when they appear simultaneously.
Operating state
The SIMATIC S7 automation systems know the following operating states: STOP,
STARTUP, RUN.
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