According to the CEI standard, %I indicates a language object of type discrete IN.

Represents an input bit.

According to the CEI standard, %IW indicates a language object of type analog IN.

Represents an input word register.

According to the CEI standard, %M indicates a language object of type memory bit.

Represents a memory bit.

According to the CEI standard, %MW indicates a language object of type memory word.

Represents a memory word register.

According to the CEI standard, %Q indicates a language object of type discrete OUT.

According to the CEI standard, %QW indicates a language object of type analog OUT.

Represents an output word register.

Represents a system bit.

According to the CEI standard, %SW indicates a language object of type system word.

Represents a system word register.

An adaptation of the IEEE 802.3 (Ethernet) standard, the 10/100 Base-T standard uses twisted-pair wiring with a maximum segment length of 100 m (328 ft) and terminates with an RJ-45 connector. A 10/100Base-T network is capable of transmitting data on normal Ethernet (10 Mbit/s) and Fast Ethernet (100 Mbits/s) networks.

A frame format, specified in the IEEE 802.3 (Ethernet) standard, in which the header specifies the data packet length.

An adapter is the target of real-time I/O data connection requests from scanners. It cannot send or receive real-time I/O data unless it is configured to do so by a scanner, and it does not store or originate the data communications parameters necessary to establish the connection. An adapter accepts explicit message requests (connected and unconnected) from other devices.

In Control Expert, advanced mode is a selection that displays expert-level configuration properties that help define Ethernet connections. Because these properties should be edited only by people with a good understanding of EtherNet/IP communication protocols, they can be hidden or displayed, depending upon the qualifications of the specific user.

Use the applicative time stamping solution to access time stamp event buffers with a SCADA system that does not support the OPC DA interface. In this case, function blocks in the Control Expert PLC application read events in the buffer and formats them to be sent to the SCADA system.

An ARRAY is a table containing elements of a single type. This is the syntax: ARRAY [<limits>] OF <Type>

Example: ARRAY [1..2] OF BOOL is a one-dimensional table with two elements of type BOOL.

ARRAY [1..10, 1..20] OF INT is a two-dimensional table with 10x20 elements of type INT.

(application response time) The time a CPU application takes to react to a given input. ART is measured from the time a physical signal in the CPU turns on and triggers a write command until the remote output turns on to signify that the data has been received.

Abstract Syntax Notation One. ASN.1 is a method for encoding/decoding messages sent between systems of different types that use different languages. It is defined by ISO standards 8824/ITU X.208 and 8825/ITU X.209.

(binary-coded decimal) Binary encoding of decimal numbers.

(boolean type) This is the basic data type in computing. A BOOL variable can have either of these values: 0 (FALSE) or 1 (TRUE).

A bit extracted from a word is of type BOOL, for example: %MW10.4.

(bootstrap protocol) A UDP network protocol that can be used by a network client to automatically obtain an IP address from a server. The client identifies itself to the server using its MAC address. The server, which maintains a pre-configured table of client device MAC addresses and associated IP addresses, sends the client its defined IP address. The BOOTP service utilizes UDP ports 67 and 68.

bootstrap protocol. A UDP/IP protocol that allows an Internet node to obtain its IP parameters based on its MAC address.

bits per second.

A bridge device connects two or more physical networks that use the same protocol. Bridges read frames and decide whether to transmit or block them based on their destination address.

A message sent to all devices in a broadcast domain.

Broadcast communications send packets from a one station to every network destination. Broadcast messages pertain to every network device or only one device for which the address is not known. (See multicast and unicast).

controller area network. The CAN protocol (ISO 11898) for serial bus networks is designed for the interconnection of smart devices (from multiple manufacturers) in smart systems for real-time industrial applications. CAN multi-master systems provide high data integrity through the implementation of broadcast messaging and advanced error detection mechanisms. Originally developed for use in automobiles, CAN is now used in a variety of industrial automation control environments.

CANopen is higher level protocol that is used in automation networks. It is based on the CAN application layer (CAL) in accordance with CiA DS 301 (EN 50325-4).

(change configuration on the fly) A feature of Control Expert that allows a module hardware change in the system configuration while the system is operating. This change does not impact active operations.

A logic RTU master or slave in an RTU module.

(common industrial protocol) A comprehensive suite of messages and services for the collection of manufacturing automation applications (control, safety, synchronization, motion, configuration and information). CIP allows users to integrate these manufacturing applications with enterprise-level Ethernet networks and the internet. CIP is the core protocol of EtherNet/IP.

A CIP transport class 1 connection used for I/O data transmission via implicit messaging between EtherNet/IP devices.

A CIP transport class 3 connection used for explicit messaging between EtherNet/IP devices.

The arrangement and interconnection of hardware components within a system and the hardware and software selections that determine the operating characteristics of the system.

In EtherNet/IP, connected messaging uses a CIP connection for communication. A connected message is a logical relationship between two or more application objects on different nodes. The connection establishes a virtual circuit in advance for a particular purpose, such as frequent explicit messages or real-time I/O data transfers.

A virtual circuit between two or more network devices, created prior to the transmission of data. After a connection is established, a series of data is transmitted over the same communication path, without the need to include routing information, including source and destination address, with each piece of data.

The EtherNet/IP network node that initiates a connection request for I/O data transfer or explicit messaging.

Describes communication between two network devices, whereby data is sent without prior arrangement between the two devices. Each piece of transmitted data also includes routing information, including source and destination address.

ConneXview is a set of configuration files to be used with HiVision 6.x network management software from Hirschmann Electronics GmbH & Co. KG. ConneXview makes it possible to manage Schneider Electric Transparent Factory devices using HiVision 6.0 or newer. ConneXview is built on the widely used simple network management protocol (SNMP).

(central processing unit) The CPU, also known as the processor or controller, is the brain of an industrial manufacturing process. It automates a process as opposed to relay control systems. CPUs are computers suited to survive the harsh conditions of an industrial environment.

(derived data type) A derived data type is a set of elements with the same type (ARRAY) or with different types (structure).

The IP address of the network or host to which all packets addressed to an unknown network or host are sent. The default gateway is typically a router or other device.

For a defined application and architecture, you can predict that the delay between an event (change of value of an input) and the corresponding change of a controller output is a finite time t, smaller than the deadline required by your process.

A Device DDT is a DDT predefined by the manufacturer and not modifiable by user. It contains the I/O language elements of an I/O module.

A user defined, unique logical personal identifier for a network device. After the Ethernet communications module is configured with a valid device name, the DHCP server uses it to identify the rack at power up.

An Ethernet-based network within a remote I/O network that contains both remote I/O and distributed I/O devices. Devices connected on this network follow specific rules to allow remote I/O determinism.

An Ethernet-based network within an RIO network that contains both RIO and distributed equipment. Devices connected on this network follow specific rules to allow RIO determinism.

(derived function block) DFB types are function blocks that can be defined by the user in ST, IL, LD or FBD language.

Using these DFB types in an application makes it possible to:

(dynamic host configuration protocol) An extension of the BOOTP communications protocol that provides for the automatic assignment of IP addressing settings, including IP address, subnet mask, gateway IP address, and DNS server names. DHCP does not require the maintenance of a table identifying each network device. The client identifies itself to the DHCP server using either its MAC address, or a uniquely assigned device identifier. The DHCP service utilizes UDP ports 67 and 68.

dynamic host configuration protocol. DHCP is a TCP/IP protocol that allows network devices (DHCP clients) to obtain their IP addresses from a DHCP server through a request to the server.

(distributed I/O) Also known as distributed equipment. DRSs use DIO ports to connect distributed equipment.

A group of distributed equipment that is not required to support RSTP. DIO clouds require only a single (non-ring) copper wire connection. They can be connected to some of the copper ports on DRSs, or they can be connected directly to the CPU or Ethernet communications modules in the local rack. DIO clouds cannot be connected to sub-rings.

A network containing distributed equipment, in which I/O scanning is performed by a CPU with DIO scanner service on the local rack. DIO network traffic is delivered after RIO traffic, which takes priority in an RIO network.

Any Ethernet device (Schneider Electric device, PC, servers, or third-party devices) that supports exchange with a CPU or other Ethernet I/O scanner service.

(domain name server/service) A service that translates an alpha-numeric domain name into an IP address, the unique identifier of a device on the network.

An alpha-numeric string that identifies a device on the internet, and which appears as the primary component of a web site’s uniform resource locator (URL). For example, the domain name schneider-electric.com is the primary component of the URL www.schneider-electric.com.

Each domain name is assigned as part of the domain name system, and is associated with an IP address.

Also called a host name.

(dual-ring switch) A ConneXium extended managed switch that has been configured to operate on an Ethernet network. Predefined configuration files are provided by Schneider Electric to downloaded to a DRS to support the special features of the main ring / sub-ring architecture.

(differentiated service code points) This 6-bit field is in the header of an IP packet to classify and prioritize traffic.

(daylight saving time) DST is also called summer time and is a practice consisting of adjusting forward the clock near the start of spring and adjusting it backward near the start of autumn.

The DT type is entered in this format:

DT#<Year>-<Month>-<Day>-<Hour>:<Minutes>:<Seconds>

(device type manager) A DTM is a device driver running on the host PC. It provides a unified structure for accessing device parameters, configuring and operating the devices, and troubleshooting devices. DTMs can range from a simple graphical user interface (GUI) for setting device parameters to a highly sophisticated application capable of performing complex real-time calculations for diagnosis and maintenance purposes. In the context of a DTM, a device can be a communications module or a remote device on the network.

See FDT.

Control Expert is the programming software for all PACs. The software includes five IEC languages that comply with IEC 61131-3. Depending on requirements, the application may use a mixture of different languages.

(electronic data sheet) EDS are simple text files that describe the configuration capabilities of a device. EDS files are generated and maintained by the manufacturer of the device.

(elementary function) This is a block used in a program which performs a predefined logical function.

A function does not have any information on the internal state. Several calls to the same function using the same input parameters will return the same output values. You will find information on the graphic form of the function call in the [functional block (instance)]. Unlike a call to a function block, function calls include only an output which is not named and whose name is identical to that of the function. In FBD, each call is indicated by a unique [number] via the graphic block. This number is managed automatically and cannot be modified.

Position and configure these functions in your program to execute your application.

You can also develop other functions using the SDKC development kit.

(elementary function block) This is a block used in a program which performs a predefined logical function.

EFBs have states and internal parameters. Even if the inputs are identical, the output values may differ. For example, a counter has an output indicating that the preselection value has been reached. This output is set to 1 when the current value is equal to the preselection value.

elementary function block. EFBs are the elementary functions and function blocks (based on C language) that can be user-customized and stored in different block libraries.

Embedded Web pages (accessed by an installed HTTP server) provide Ethernet communications modules with easy access to devices anywhere in the world from standard browsers such as Internet Explorer or Netscape Navigator.

electromagnetic compatibility. Devices that meet EMC requirements can operate within a system’s expected electromagnetic limits.

EN stands for ENable; it is an optional block input. When the EN input is enabled, an ENO output is set automatically.

If EN = 0, the block is not enabled; its internal program is not executed, and ENO is set to 0.

If EN = 1, the block's internal program is run and ENO is set to 1. If a runtime error is detected, ENO is set to 0.

If the EN input is not connected, it is set automatically to 1.

ENO stands for Error NOtification; this is the output associated with the optional input EN.

A 10 Mb/s, 100 Mb/s, or 1 Gb/s, CSMA/CD, frame-based LAN that can run over copper twisted pair or fiber optic cable, or wireless. The IEEE standard 802.3 defines the rules for configuring a wired Ethernet network; the IEEE standard 802.11 defines the rules for configuring a wireless Ethernet network. Common forms include 10BASE-T, 100BASE-TX, and 1000BASE-T, which can utilize category 5e copper twisted pair cables and RJ45 modular connectors.

A LAN cabling and signaling specification used to connect devices within a defined area, e.g., a building. Ethernet uses a bus or a star topology to connect different nodes on a network.

This embedded DIO scanner service of M580 CPUs manages distributed equipment on an M580 device network.

This embedded Ethernet I/O scanner service of M580 CPUs manages distributed equipment and RIO drops on an M580 device network.

A frame format in which the header specifies the packet type, Ethernet II is the default frame format for STB NIP 2212 communications.

A network communication protocol for industrial automation applications that combines the standard internet transmission protocols of TCP/IP and UDP with the application layer common industrial protocol (CIP) to support both high speed data exchange and industrial control. EtherNet/IP employs electronic data sheets (EDS) to classify each network device and its functionality.

TCP/IP-based messaging for Modbus TCP and EtherNet/IP. It is used for point-to-point, client/server messages that include both data, typically unscheduled information between a client and a server, and routing information. In EtherNet/IP, explicit messaging is considered class 3 type messaging, and can be connection-based or connectionless.

(explicit messaging client class) The device class defined by the ODVA for EtherNet/IP nodes that only support explicit messaging as a client. HMI and SCADA systems are common examples of this device class.

The fast (FAST) task is a periodic, high-priority task of a short duration that is run on a processor through its programming software. The fast speed of the task keeps it from interfering with the execution of lower priority master (MAST) tasks. A FAST task is useful when fast periodic changes in discrete inputs need to be monitored.

(function block diagram) An IEC 61131-3 graphical programming language that works like a flowchart. By adding simple logical blocks (AND, OR, etc.), each function or function block in the program is represented in this graphical format. For each block, the inputs are on the left and the outputs on the right. Block outputs can be linked to inputs of other blocks to create complex expressions.

(fast device replacement) A service that uses configuration software to replace an inoperable product.

The fast device replacement service offers a method of handling device replacement without disrupting the system nor interrupting service.

(field device tool) The technology that harmonizes communication between field devices and the system host.

Flash memory is nonvolatile memory that can be overwritten. It is stored on a special EEPROM that can be erased and reprogrammed.

A frame is a group of bits that form a discrete block of information. Frames contain network control information or data. The size and composition of a frame is determined by the network technology being used.

Two common framing types for Ethernet are Ethernet II and IEEE 802.3.

(file transfer protocol) A protocol that copies a file from one host to another over a TCP/IP-based network, such as the internet. FTP uses a client-server architecture as well as separate control and data connections between the client and server.

File Transfer Protocol. FTP is the World Wide Web’s file transfer protocol.

The ability of two networked devices to independently and simultaneously communicate with each other in both directions.

See FBD.

A gateway device interconnects two different networks, sometimes through different network protocols. When it connects networks based on different protocols, a gateway converts a datagram from one protocol stack into the other. When used to connect two IP-based networks, a gateway (also called a router) has two separate IP addresses, one on each network.

A device that connects networks with dissimilar network architectures and which operates at the Application Layer of the OSI model. This term may refer to a router.

Global Data provides the automatic exchange of data variables for the coordination of PLC applications.

GARP multicast registration protocol. GMRP is a GARP (Generic Attribute Registration Protocol) application that allows switches and bridges to dynamically manage the membership of multicast groups. GMRP is defined by IEEE 802.1D.

(global positioning system) The GPS standard consists of a space-based positioning, navigation, and timing signals delivered worldwide for civil and military use. Standard positioning service performance depends on satellite broadcast signal parameters, GPS constellation design, the number of satellites in sight, and various environmental parameters.

A method of data transmission capable of communication in either of two directions, but in only one direction at a time.

Resistance to hydrocarbons, industrial oils, detergents and solder chips. Relative humidity up to 100%, saline atmosphere, significant temperature variations, operating temperature between ‑10°C and + 70°C, or in mobile installations. For hardened (H) devices, the relative humidity is up to 95% and the operating temperature is between ‑25°C and + 70°C.

(highway addressable remote transducer) A bi-directional communication protocol for sending and receiving digital information across analog wires between a control or monitoring system and smart devices.

HART is the global standard for providing data access between host systems and intelligent field instruments. A host can be any software application from a technician's hand-held device or laptop to a plant's process control, asset management, or other system using any control platform.

Often referred to as HCDL, a high-capacity daisy chain loop uses dual-ring switches (DRSs) to connect device sub-rings (containing RIO drops or distributed equipment) and/or DIO clouds to the Ethernet RIO network.

(human machine interface) System that allows interaction between a human and a machine.

human-machine interface. An operator interface, usually graphical, for industrial equipment.

A Hot Standby system uses a primary PAC (PLC) and a standby PAC. The two PAC racks have identical hardware and software configurations. The standby PAC monitors the current system status of the primary PAC. If the primary PAC becomes inoperable, high-availability control is maintained when the standby PAC takes control of the system.

Replacing a component with a like component while the system remains operational. When the replacement component is installed, it begins to function automatically.

(hypertext transfer protocol) A networking protocol for distributed and collaborative information systems. HTTP is the basis of data communication for the web.

HyperText Transfer Protocol. HTTP is the protocol for the formatting and transmission of files on the world wide web. HTTP runs on top of TCP/IP (Internet) protocols.

The installed HTTP server transmits Web pages between a server and a browser, providing Ethernet communications modules with easy access to devices anywhere in the world from standard browsers such as Internet Explorer or Netscape Navigator.

A hub device connects a series of flexible and centralized modules to create a network.

In a programmable controller system, an I/O module interfaces directly to the sensors and actuators of the machine/process. This module is the component that mounts in an I/O base and provides electrical connections between the controller and the field devices. Normal I/O module capacities are offered in a variety of signal levels and capacities.

A configuration table which identifies the targets with which repetitive communication is authorized.

An Ethernet service that continuously polls I/O modules to collect data, status, event, and diagnostics information. This process monitors inputs and controls outputs. This service supports both RIO and DIO logic scanning.

An I/O scan continuously polls I/O modules to collect data bits and status and diagnostics information. This process monitors inputs and control outputs.

Internet Control Message Protocol. ICMP is a protocol within TCP/IP that reports detected errors in datagram transmissions.

International standard: programmable logic controllers

Part 3: programming languages

Institute of Electrical and Electronics Engineers, Inc. The international standards and conformity assessment body for all fields of electrotechnology, including electricity and electronics.

(internet group management protocol) This internet standard for multicasting allows a host to subscribe to a particular multicast group.

(instruction list) An IEC 61131-3 programming language that contains a series of basic instructions. It is very close to assembly language used to program processors. Each instruction is made up of an instruction code and an operand.

UDP/IP-based class 1 connected messaging for EtherNet/IP. Implicit messaging maintains an open connection for the scheduled transfer of control data between a producer and consumer. Because an open connection is maintained, each message contains primarily data, without the overhead of object information, plus a connection identifier.

(INTeger) (encoded in 16 bits) The upper/lower limits are as follows: -(2 to the power of 15) to (2 to the power of 15) - 1.

Example: -32768, 32767, 2#1111110001001001, 16#9FA4.

An Ethernet-based network that is part of the control network, and provides data exchange between controllers and engineering tools (programming, asset management system (AMS)).

information object access. IOA is the exchange protocol carried out over the HTTP (HyperText Transfer Protocol) channel.

(input/output derived data type) A structured data type representing a module, or a channel of a CPU. Each application expert module possesses its own IODDTs.

input/output derived data type. IODDT is a structured data type representing a module or a channel of a PLC module. Each application expert module possesses its own IODDTs.

Internet protocol. That part of the TCP/IP protocol family that tracks the Internet addresses of nodes, routes outgoing messages, and recognizes incoming messages.

The 32-bit identifier, consisting of both a network address and a host address assigned to a device connected to a TCP/IP network.

Internet protocol address. This 32-bit address is assigned to hosts that use TCP/IP.

(internet protocol security) An open set of protocol standards that make IP communication sessions private and secure for traffic between modules using IPsec, developed by the internet engineering task force (IETF). The IPsec authentication and encryption algorithms require user-defined cryptographic keys that process each communications packet in an IPsec session.

An Ethernet-based network containing distributed equipment that does not participate in an RIO network.

local area network. A short-distance data communications network.

In the OSI model, a layer is a portion of the structure of a device that provides defined services for the transfer of information.

(ladder diagram) An IEC 61131-3 programming language that represents instructions to be executed as graphical diagrams very similar to electrical diagrams (contacts, coils, etc.).

light emitting diode. An indicator that lights up when electricity passes through it. It indicates the operation status of a communications module.

A literal value of an integer is used to enter integer values in the decimal system. Values may be preceded by the "+" and "-" signs. Underscore signs (_) separating numbers are not significant.

Example:

-12, 0, 123_456, +986

An M580 rack containing the CPU and a power supply. A local rack consists of one or two racks: the main rack and the extended rack, which belongs to the same family as the main rack. The extended rack is optional.

The functionality offered by Schneider Electric EtherNet/IP communication modules that allows a scanner to take the role of an adapter. The local slave enables the module to publish data via implicit messaging connections. Local slave is typically used in peer-to-peer exchanges between PACs.

media access control address. A 48-bit number, unique on a network, that is programmed into each network card or device when it is manufactured.

The main ring of an Ethernet RIO network. The ring contains RIO modules and a local rack (containing a CPU with Ethernet I/O scanner service) and a power supply module.

(Modbus over TCP protocol) This is a Modbus variant used for communications over TCP/IP networks.

(management information base) A virtual database used for managing the objects in a communications network. See SNMP.

management information base. The MIB is an object database that is monitored by a network management system like SNMP. SNMP monitors devices that are defined by their MIBs. Schneider has obtained a private MIB, groupeschneider (3833).

Modbus is an application layer messaging protocol. Modbus provides client and server communications between devices connected on different types of buses or networks. Modbus offers many services specified by function codes.

A special form of broadcast where copies of the packet are delivered to only a specified subset of network destinations. Implicit messaging typically uses multicast format for communications in an EtherNet/IP network.

Multicast communications send packets from a single source to a predefined multicast group of network destinations, usually through a router or switch. Sending messages to just the group members relieves unnecessary traffic created by broadcast communications and does not require a separate unicast transmissions to each recipient. (See broadcast, unicast, GMRP.)

Multicast filtering is a process for deciding that multicast messages are delivered only to the stations that are registered members of the appropriate multicast group.

Use this service to synchronize computer clocks over the Internet to record events (sequence events), synchronize events (trigger simultaneous events), or synchronize alarms and I/O (time stamp alarms).

(network interface module) A NIM resides in the first position on an STB island (leftmost on the physical setup). The NIM provides the interface between the I/O modules and the fieldbus master. It is the only module on the island that is fieldbus-dependent — a different NIM is available for each fieldbus.

network management. NMT protocols provide services for network initialization, diagnostics, and device status control.

(network time protocol) Protocol for synchronizing computer system clocks. The protocol uses a jitter buffer to resist the effects of variable latency.

network time protocol. NTP synchronizes the time of one client or server to the time of another server or referenced source (such as a satellite receiver).

(originator to target) See originator and target.

(Open DeviceNet Vendors Association) The ODVA supports network technologies that are based on CIP.

(OPC Factory Server) OFS enables real-time SCADA communications with the Control Expert family of PLCs. OFS utilizes the standard OPC data access protocol.

(OLE for Process Control Data Access) The Data Access Specification is the most commonly implemented of the OPC standards that provide specifications for real-time data communications between clients and servers.

An Ethernet-based network containing operator tools (SCADA, client PC, printers, batch tools, EMS, etc.). Controllers are connected directly or through routing of the inter-controller network. This network is part of the control network.

In EtherNet/IP, a device is considered the originator when it initiates a CIP connection for implicit or explicit messaging communications or when it initiates a message request for un-connected explicit messaging.

Open Systems Interconnection model. The OSI reference model is the abstract seven-layer model for establishing logical communications and protocol design. The model was developed by the International Standards Organization (ISO).

programmable automation controller. The PAC is the brain of an industrial manufacturing process. It automates a process as opposed to relay control systems. PACs are computers suited to survive the harsh conditions of an industrial environment.

programmable automation controller The PAC is the brain of an industrial manufacturing automation process. It automates a process as opposed to relay control systems. PACs are computers suited to survive the harsh conditions of the industrial environment.

The unit of data sent across a network.

packet Internet groper. A PING program tests communications to another network destination.

PL7 software from Telemecanique is a programming language for TSX Micro and Modicon Premium PLCs.

programmable logic controller. The PLC is the brain of an industrial manufacturing process. It automates a process as opposed to relay control systems. PLCs are computers suited to survive the harsh conditions of the industrial environment.

Port 502 of the TCP/IP stack is the well-known port that is reserved for Modbus TCP communications.

TCP/IP reserves specific server ports for specific applications through IANA (Internet Assigned Numbers Authority). Modbus requests are sent to registered software port 502.

In this mode, data traffic that is related to the source port on a network switch is copied to another destination port. This allows a connected management tool to monitor and analyze the traffic.

Schneider has obtained a private MIB, groupeschneider (3833). Under the Groupe Schneider private MIB is a Transparent Factory Ethernet (TFE) private MIB. The Transparent Factory SNMP embedded component controls the Schneider private MIB function. This MIB includes a set of data that enables the network management system to supervise all the Transparent Ready services. The Transparent Ready private MIB can be downloaded from the Web server.

(precision time protocol) Use this protocol to synchronize clocks throughout a computer network. On a local area network, PDP achieves clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems.

A Global Data variable that is published.

(quality of service) The practice of assigning different priorities to traffic types for the purpose of regulating data flow on the network. In an industrial network, QoS is used to provide a predictable level of network performance.

Data from multiple I/O modules are consolidated in a single data packet to be presented to the scanner in an implicit message in an EtherNet/IP network.

Ethernet ready device that provides additional services to the EtherNet/IP or Modbus module, such as: single parameter entry, bus editor declaration, system transfer, deterministic scanning capacity, alert message for modifications, and shared user rights between Control Expert and the device DTM.

One of the three types of RIO modules in an Ethernet RIO network. An RIO drop is an M580 rack of I/O modules that are connected to an Ethernet RIO network and managed by an Ethernet RIO adapter module. A drop can be a single rack or a main rack with an extended rack.

An Ethernet-based network that contains 3 types of RIO devices: a local rack, an RIO drop, and a ConneXium extended dual-ring switch (DRS). Distributed equipment may also participate in an RIO network via connection to DRSs or BMENOS0300 network option switch modules.

A router device connects two or more sections of a network and allows information to flow between them. A router examines every packet it receives and decides whether to block the packet from the rest of the network or transmit it. The router attempts to send the packet through the network on an efficient path.

(requested packet interval) The time period between cyclic data transmissions requested by the scanner. EtherNet/IP devices publish data at the rate specified by the RPI assigned to them by the scanner, and they receive message requests from the scanner at each RPI.

(rapid spanning tree protocol) Allows a network design to include spare (redundant) links to provide automatic backup paths if an active link stops working, without the need for loops or manual enabling/disabling of backup links.

Remote Terminal Unit.

A Quantum RIO system using coaxial cabling and terminators.

(supervisory control and data acquisition) SCADA systems are computer systems that control and monitor industrial, infrastructure, or facility-based processes (examples: transmitting electricity, transporting gas and oil in pipelines, and distributing water).

A scanner acts as the originator of I/O connection requests for implicit messaging in EtherNet/IP, and message requests for Modbus TCP.

A scanner class device is defined by the ODVA as an EtherNet/IP node capable of originating exchanges of I/O with other nodes in the network.

The Transparent Ready service classes thus simplify the choice of products and check their interoperability within an architecture.

(sequential function chart) An IEC 61131-3 programming language that is used to graphically represent in a structured manner the operation of a sequential CPU. This graphical description of the CPU's sequential behavior and of the various resulting situations is created using simple graphic symbols.

(small form-factor pluggable). The SFP transceiver acts as an interface between a module and fiber optic cables.

Often referred to as SDCL, a simple daisy chain loop contains RIO modules only (no distributed equipment). This topology consists of a local rack (containing a CPU with Ethernet I/O scanner service), and one or more RIO drops (each drop containing an RIO adapter module).

(simple mail transfer protocol) An email notification service that allows controller-based projects to report alarms or events. The controller monitors the system and can automatically create an email message alert with data, alarms, and/or events. Mail recipients can be either local or remote.

Simple Mail Transfer Protocol. SMTP is a transmission protocol for sending and receiving e-mail. SMTP messages are usually retrieved from a server with an e-mail client (such as POP or IMAP).

(simple network management protocol) Protocol used in network management systems to monitor network-attached devices. The protocol is part of the internet protocol suite (IP) as defined by the internet engineering task force (IETF), which consists of network management guidelines, including an application layer protocol, a database schema, and a set of data objects.

simple network management protocol. The UDP/IP standard protocol used to monitor and manage devices on an IP network.

The SNMP application that runs on a network device.

(simple network time protocol) See NTP.

(sequence of events) SOE software helps users understand a chain of occurrences that can lead to unsafe process conditions and possible shutdowns. SOEs can be critical to resolving or preventing such conditions.

(structured text) An IEC 61131-3 programming language that presents structured literal language and is a developed language similar to computer programming languages. It can be used to organize a series of instructions.

A Global Data variable that is defined as a subscription variable.

An Ethernet-based network with a loop attached to the main ring, via a dual-ring switch (DRS) or BMENOS0300 network option switch module on the main ring. This network contains RIO or distributed equipment.

The subnet is that portion of the network that shares a network address with the other parts of the network. A subnet may be physically or logically independent from the rest of the network. A part of an Internet address called a subnet number, which is ignored in IP routing, distinguishes the subnet.

The 32-bit value used to hide (or mask) the network portion of the IP address and thereby reveal the host address of a device on a network using the IP protocol.

The subnet mask is a bit mask that identifies or determines which bits in an IP address correspond to the network address and which correspond to the subnet portions of the address. The subnet mask comprises the network address plus the bits reserved for identifying the subnetwork.

A multi-port device used to segment the network and limit the likelihood of collisions. Packets are filtered or forwarded based upon their source and destination addresses. Switches are capable of full-duplex operation and provide full network bandwidth to each port. A switch can have different input/output speeds (for example, 10, 100 or 1000Mbps). Switches are considered OSI layer 2 (data link layer) devices.

A network switch connects two or more separate network segments and allows traffic to be passed between them. A switch determines whether a frame should be blocked or transmitted based on its destination address.

(target to originator) See target and originator.

In EtherNet/IP, a device is considered the target when it is the recipient of a connection request for implicit or explicit messaging communications, or when it is the recipient of a message request for un-connected explicit messaging.

(transmission control protocol) A key protocol of the internet protocol suite that supports connection-oriented communications, by establishing the connection necessary to transmit an ordered sequence of data over the same communication path.

Also known as internet protocol suite, TCP/IP is a collection of protocols used to conduct transactions on a network. The suite takes its name from two commonly used protocols: transmission control protocol and internet protocol. TCP/IP is a connection-oriented protocol that is used by Modbus TCP and EtherNet/IP for explicit messaging.

Transmission Control Protocol/Internet Protocol. TCP/IP is the communication protocol of the Internet.

transparent factory Ethernet. Schneider Electric’s open automation framework based on TCP/IP.

(trivial file transfer protocol) A simplified version of file transfer protocol (FTP), TFTP uses a client-server architecture to make connections between two devices. From a TFTP client, individual files can be uploaded to or downloaded from the server, using the user datagram protocol (UDP) for transporting data.

Trivial File Transfer Protocol. TFTP is a scaled-down version of FTP that uses UDP, often to initialize diskless workstations.

See TOD.

The TOD type is entered in this format: xxxxxxxx: TOD#<Hour>:<Minutes>:<Seconds>

Example: TOD#23:59:45.

(transparent ready) Web-enabled power distribution equipment, including medium- and low-voltage switch gear, switchboards, panel boards, motor control centers, and unit substations. Transparent Ready equipment allows you to access metering and equipment status from any PC on the network, using a standard web browser.

Transparent Device Access (TDA) functionality means that clients that run Control Expert (and that are connected to a USB, Ethernet, or Modbus terminal port of a communications module) can access or download applications to devices on distributed control networks. The reverse, however, is not true. In other words, a Control Expert PC connected to the CPU’s Modbus port can access devices on other core networks, but those remote devices can not access other devices on different networks through the PLC station.

See TFE.

Schneider Electric’s Transparent Ready products (based on universal Ethernet TCP/IP and Web technologies) can be integrated into real-time, data sharing systems, with no need for interfaces.

(user datagram protocol) A transport layer protocol that supports connectionless communications. Applications running on networked nodes can use UDP to send datagrams to one another. Unlike TCP, UDP does not include preliminary communication to establish data paths or provide data ordering and checking. However, by avoiding the overhead required to provide these features, UDP is faster than TCP. UDP may be the preferred protocol for time-sensitive applications, where dropped datagrams are preferable to delayed datagrams. UDP is the primary transport for implicit messaging in EtherNet/IP.

user datagram protocol. UDP is an Internet communications protocol defined by IETF RFC 768. This protocol facilitates the direct transmission of datagrams on IP networks. UDP/IP messages do not expect a response, and are therefore ideal for applications in which dropped packets do not require retransmission (such as streaming video and networks that demand real-time performance).

(Unified Messaging Application Services) UMAS is a proprietary system protocol that manages communications between Control Expert and a controller.

Unicast communications send point-to-point packets from a single source to a specific network destination. It is an efficient means of communication between hosts that has a minimal impact on network traffic. (See broadcast and multicast.)

Unity Pro is the programming software for all Unity PLCs. It includes 5 IEC languages that comply with IEC 61131-3. Depending on requirements, the application may use a mixture of different languages.

universal serial bus. USB is a nearly universal hardware interface for connecting peripheral devices.

(coordinated universal time) Primary time standard used to regulate clocks and time worldwide (close to former GMT time standard).

Memory entity of type BOOL, WORD, DWORD, etc., whose contents can be modified by the program currently running.

A variable is a memory entity of the type BOOL, WORD, DWORD, etc., whose contents can be modified by the program during execution.

(virtual local area network) A local area network (LAN) that extends beyond a single LAN to a group of LAN segments. A VLAN is a logical entity that is created and configured uniquely using applicable software.