8. Glossary
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8. Glossary
In a redundant system, the Active CPU performs the system control, reading the input points values,
executing the applicative program and driving the output values.
POU from the program type, created automatically, which should be completed by the user. It runs only
on the Active PLC, and used to control the automated process.
Strategy to facilitate the connection of Ethernet clients to Ethernet servers executed on a redundant PLC.
Half-cluster (PLCA or PLCB) which is momentarily in Active state.
Address or configuration selecting switch composed by pins present in the circuit board and a small
removable connector, used for selecting.
The variable can be accessed directly in the memory using the desired address. E.g. QB0%, %MW100.
Part of the project corresponding to the executable code.
It’s the program loaded into a PLC, which determines the operation of a machine or process.
Reserved words in the programming software, used to indicate diagnostics.
Electric signals cluster logically grouped with the function to transmit information and control between
different elements of a sub-system.
Basic information unit which can assume state 0 or 1.
Time the network node type CSMA/CD waits before re-transmit data after the occurrence of collisions in
the physical environment.
Rate at which information bits are transmitted via a serial interface or communications network
(measured in bits/second).
Equipment for connecting two communication networks within the same protocol.
Dissemination of information simultaneously to all nodes connected to a communication network.
Information unit composed by 8 bits.
One of the UTP cable categories:. Unshielded twisted-pair 100 ohm impedance and electrical
characteristics supporting up to 100 MHz transmission frequency defined by the TIA / EIA 568-A, can be
used in 10Base-T and 100Base networks TX, among others.
Set formed by the controllers (half-clusters) PLCA and PLCB.
Product code, formed by the PO letters followed by four numbers.
Group of devices (nodes) interconnected by communication channels.
Also called a module C. It is a single module in a PLC program that contains various parameters required
to the controller functioning, such as the amount of variables and layout of the I/O modules in the bus.
Abbreviation for central processing unit. Controls the information flow, interprets and executes program
instructions and monitors the devices in the system.
Physical layer access protocol, based in data collision, used for Ethernet networks.
It is the time that the CPU takes to run a particular application task.
Pre-defined value for a variable, used in case there’s no definition.
Deterministic
Communication
Network
Communication network where the transmission and reception of information between different nodes is
guaranteed with a maximum known time.
Procedure used to detect and isolate failures. It’s also the data group used for such determination, which
serves for problem analysis and correction.
Direct Representation
Variable
The variable can be accessed directly in memory, using a web address. For example:% QB0,% MW100.
Used abbreviation to indicate diagnostics in the LEDs
Program or configuration load in the PLC.
Industrial pattern (physical layer) for data communication.
In PROFIBUS networks, it’s the standard which defines the fieldbus.
An information unit transmitted through the network.
In PROFIBUS networks, it’s the network state when the input data are frozen.
Indicates that the devices can perform communication by transmitting / receiving data in both directions
simultaneously, i.e. it can transmit and receive at the same time.
Equipment for connecting two networks with different communication protocols.
Connector normally connected to the parallel interface of a PC in order to avoid the execution of software
illegal copies.
Physical equipment used in data processing where the programs (software) are executed.
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