O - R

Original Equipment Manufacturer (OEM)

An organization that makes devices from component parts bought from other organizations.

OEM parameter

Parameters attached to an I/O module. A parameter is characterized by a type. An OEM parameter is defined by the designer of the controller. It can be a constant, or a variable parameter entered by the user during the I/O connection.

online mode

Mode in which the application is connected to a target and the application code is executed.

Open Platform Communications (OPC)

A series of standards and specifications for industrial communication. An industrial automation task force developed the original standard in 1996 under the name OLE for Process Control (Object Linking and Embedding for process control). OPC specifies the communication of real-time plant data between control devices from different manufacturers.

operator

Basic logical operation such as arithmetic, boolean, comparator, and data conversion.

output

The direction of a variable or a device. An output variable is connected to an output channel of an output device.

output parameter

Data that is produced as a direct result of executing an instruction or function.

overflow

Integer value which corresponds to the number of times the cycle time has been exceeded. Always 0, if cycle time is 0.

parent program

A program which controls other programs, called its children.

peer-to-peer

One or more Ethernet networks connecting a series of devices together enabling application data to pass between them.

ping

A signal sent across a communication channel, used as a diagnostic query data command over a link and then receiving a a reply ensuring the link is healthy and that communications can occur. No process data is transfered or modified.

programmable logic controller (PLC)

An industrial digital computer which has been adapted for reliability in harsh conditions and is dedicated to the control of manufacturing processes.

plug-in

A module or package integrated into a bigger platform that enables the extension of the application.

Program Organization Unit (POU)

A set of instructions that are programs, functions or function blocks.

power rail

Main left and right vertical rails at the extremities of a ladder diagram.

producer

A controller producing a tag to one or more consumers requesting one.

program

A program executes a set of instructions in a project.

project

A set of controllers and links between their programs.

protocol

A set of communication rules used for communications across devices.

process safety time (PST)

The process safety time, for the equipment in use, is the length of time a dangerous condition can be present before a hazardous event occurs without the protection of a safety system.

pulse action

A list of statements executed only once when the corresponding step is activated.

qualifier

Determines the way the action of a step is executed.

REAL

Type of a variable, stored in a floating IEEE single precision 32-bit format. Basic type that can be used to define a variable, a Parameter or a Controller.

real-time mode

The run time normal execution mode of a controller where target cycles are triggered by the cycle timing. Another execution mode for controllers is cycle-to-cycle mode.

redundancy

The use of two or more controllers, each carrying out the same function, to improve reliability or availability.

redundant group

A group containing the same type of I/O modules arranged in parallel for a group of I/O channels. This configuration increases fault tolerance for I/O data.

retain

The attribute of a variable. The value of a retain variable is saved at each cycle. The value is restored during stops and restarts.

return

Graphic component of a program representing the conditional end of a program.

return parameter

An output parameter that uses a method called

return-by-value

allowing the values to be read by the calling instance (an instance of a program or Function Block).

rich text

Text formatting that includes, for example, bold, italic, underline, strikethrough, and justification, and is applied with the Description Editor toolbar.

rising edge

The transition of a value from low to high. For example, when applied to a Boolean variable it corresponds to a change from FALSE (0) to TRUE (1).

real-time clock (RTC)

A clock internal to the computer that keeps track of the current time in human units; year, month, date, hours, minutes, and seconds, providing an accurate date and time allowing the computer to regulate the timing and speed of various functions.

remote terminal unit (RTU)

A computing device used in industrial control systems for remote monitoring and control of various automation devices and systems.

run-time engine

The embedded software that solves application logic and drive I/O points.

run-time error

An error that occurs in the program when it is executed.

rung

The graphic component of an Ladder Diagram program representing a group of circuit elements leading to the activation of a coil in an Ladder Diagram.