Machine Automation Controllers

AT Specification

One of the attributes of a variable.
This attribute allows the user to specify what is assigned to a variable.
An I/O port or an address in memory used for CJ-series Units can be specified.

FB

An acronym for "function block."

FUN

An abbreviation for "function."

I/O Port

A logical interface that is used by the CPU Unit to exchange data with an external device (slave or Unit).

I/O Map Settings

Settings that assign variables to I/O ports.
Assignment information between I/O ports and variables.

PDO Communications

An abbreviation for process data communications. Data is exchanged between the master and slaves on a process data communications cycle. (The process data communications cycle is the same as the task period of the primary periodic task.)

POU (Program Organization Unit)

A POU is a unit in a program execution model that is defined in IEC 61131-3. It contains an algorithm and a local variable table and forms the basic unit used to build a user program.
There are three types of POUs: programs, functions, and function blocks.

SDO Communications

One type of EtherCAT communications in which service data objects (SDOs) are used to transmit information whenever required.

Basic Data Type

Any of the data types that are defined by IEC 61131-3.
They include Boolean, bit string, integer, real, duration, date, time of day, date and time, and text string data types.
"Basic data type" is used as opposed to derivative data types, which are defined by the user.

Union

One of the derivative data types. It allows you to handle the same data as different data types.

Global Variable

A variable that can be read or written from all POUs
(programs, functions, and function blocks).

Structure

One of the derivative data types. It consists of multiple data types placed together into a layered structure.

Constant

One of the attributes of a variable.
If you specify the Constant attribute for a variable, the value of the variable cannot be written by any instructions, ST operators, or CIP message communications.

Axis

A functional unit within the Motion Control Function Module.
An axis is assigned to the drive mechanism in an external Servo Drive or the sensing mechanism in an external Encoder Input Slave Unit.

Axes Group

A functional unit that groups together axes within the Motion Control Function Module.

Axes Group Variable

A system-defined variable that is defined as a structure and provides status information and some of the axes parameters for an individual axes group.
An Axes Group Variable is used to specify an axes group for motion control instructions and to monitor the command interpolation velocity, error information, and other information for the axes group.

Axis Variable

A system-defined variable that is defined as a structure and provides status information and some of the axis parameters for an individual axis.
An Axis Variable is used to specify an axis for motion control instructions and to monitor the command position, error information, and other information for the axis.

System-defined Variable

A variable for which all attributes are defined by the system and cannot be changed by the user.

Initial Value

One of the attributes of a variable.
The variable is set to the initial value in the following situations.
• When power is turned ON
• When the CPU Unit changes to RUN mode
• When you specify to initialize the values when the user program is transferred
• When a major fault level Controller error occurs

Task

An attribute that defines when a program is executed.

Task Period

The interval at which the primary periodic task or a periodic task is executed.

Periodic Task

A task for which user program execution and I/O refreshing are performed each period.

Device Variable

A task for which user program execution and I/O refreshing are performed each period.

Namespace

A system that is used to group and nest the names of functions, function block definitions, and data types.

Network Publish

One of the attributes of a variable.
This attribute allows you to use CIP message communications or tag data links to read/write variables from another Controller or from a host computer.

Array Specification

One of the variable specifications.
An array variable contains multiple elements of the same data type. The elements in the array are specified by serial numbers called subscripts that start from the beginning of the array.

Derivative Data Type

A data type that is defined by the user.
Structures, unions, and enumerations are derivative data types.

Function

A POU that is used to create an object that determines a unique output for the same input, such as for data processing.

Function Block

A POU that is used to create an object that can have a different output for the same input, such as for a timer or counter.

Primary Periodic Task

The task with the highest priority.

Program

One of three POUs. The others are functions and function blocks.
Programs are assigned to tasks to execute them.

Process Data Communications

One type of EtherCAT communications in which process data objects (PDOs) are used to exchange information cyclically and in realtime. It is also called "PDO communications.".

Variable

A representation of data, such as a numeric value or character string, that is used in a user program.
You can change the value of a variable by assigned the required value. "Variable" is used as opposed to "constant," for which the value does not change.

Variable Memory

A memory area that contains the present values of variables that do not have AT specifications.
It can be accessed only with variables without an AT attribute.

Retain

One of the attributes of a variable.
The values of variables with a Retain attribute are held at the following times. (Variables without a Retain attribute are set to their initial values.)
• When power is turned ON after a power interruption
• When the CPU Unit changes to RUN mode
• When you specify to not initialize the values when the user program is transferred

Motion Control Instruction

A function block instruction that executes motion control.
The Motion Control Function Module supports instructions that are based on function blocks for PLCopen® motion control as well as instructions developed specifically for the Motion Control Function Module.

User-defined Variable

A variable for which all of the attributes are defined by the user and can be changed by the user.

Literal

A constant expression that is used in a user program.

Enumeration

One of the derivative data types.
This data type takes one item from a prepared name list of enumerators as its value.

Enumerator

One of the values that an enumeration can take expressed as a character string.
The value of an enumeration is one of the enumerators.

Local Variable

A variable that can be accessed only from inside the POU in which it is defined.
"Local variable" is used as opposed to "global variable." Local variables include internal variables, input variables, output variables, in-out variables, and external variables.