Parameter/Local Tag Properties dialog box
Use this Properties dialog box to update the properties of an Add-On Instruction definition.
Note that the controls on this dialog box are unavailable if the Add-On Instruction is sealed or is source-protected.
Attributes
Name
Enter a name following the
Logix Designer
application IEC-1131 naming standard. If a Parameter or Local Tag of the same name already exists in this Instruction Definition, an error dialog box displays when you click OK or Apply.
IEC-61131 Name Standard
(The names are composed per IEC-61131, section 2.1.2.)
An identifier is a string of letters, digits, and underline characters that begin with a letter or underline character. Underlines are significant in identifiers (for example, A_BCD is interpreted differently than AB_CD). Multiple leading or multiple (consecutive) embedded underlines are not allowed, trailing underlines are not allowed, and letter case is not considered significant.
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In Logix Designer, most component names are limited in length to 40
characters or less.
Description
You can modify the description for the Parameter or Local Tag.
Usage
Click the pull-down menu to set the usage of the Parameter or Local Tag. The valid options are as follows.
- Input parameterinput parameterFor an Add-On Instruction, an input parameter defines data that is passed into the instruction. The value is passed to the instruction before execution. The parameter's value is also accessible through a member of a tag, which is of the Add-On Instruction's data type. An input parameter also holds a value designed to specify how a sequence or procedure is to execute. Input Parameters can accept a literal value or a tag as an argument. The data type of an input parameter can be any valid atomic data type.
- Output parameteroutput parameterData that is produced as a direct result of executing an instruction or function.
- InOut parameterInOut ParameterFor an Add-On Instruction, an InOut Parameter defines data that is used as both input and output during the execution of the instruction. An InOut Parameter is passed by reference, meaning the logic deals directly with the tag passed to the instruction. InOut parameters can be any valid data type because they are passed by reference. This includes message, motion group, all axis, and module data types. Any data structures or arrays that need to be passed to an Add-On Instruction must be done using InOut parameters.
- Local Tag - Local Tags are private to the Add-On Instruction. They cannot be accessed by external logic.Local tagFor an Add-On Instruction, Local tags are used strictly by the instruction and not the user of the instruction. As such, Local tags are not available as members in the data structure when a tag is of the Add-On Instruction data type. Local tags are typically used for instructions internal to the Add-On Instruction or for tags that are used as retentive intermediate values in some operation. Local tags can be viewed only from within the Add-On Instruction definition.
Your Usage selection determines if you can make the Parameter required or visible.
Alias For
If a tag is an alias, this column shows the target tag (tag that contains the data type definition for an alias tag). The cell has a drop-down button that displays the Tag Browser.
This column is not available for Add-On Instruction definition context.
Data Type
To select a data type, click the ellipses to access the
Select Data Type
dialog box.
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- Data types are restricted for safety Add-on Instructions.
- Input and Output parameters can be atomic data types only. Input and Output parameters are passed, during an Add-On Instruction call, by-value. InOut parameters can be atomic or complex (that is, structures or arrays) data types. InOut parameters are always passed by-reference.
The Data Type field appears dimmed for members of the InOut parameters.
The data type for a Local Tag cannot be a multi-dimensional array or an object type, which includes all Motion types, MSG, ALARM_ANALOG, and ALARM_DIGITAL.
The Data Type field appears dimmed for members of a Local Tag.
Instruction
A read-only field identifying the Instruction name in which the Parameter or Local Tag is defined. The icon indicates if the instruction is standard or
safety.
Add-On Instruction
An instruction that is defined as an add-on to the Logix defined instruction set. Once defined, an Add-On Instruction can be used like any system-defined instruction and can be used across various projects. An Add-On Instruction is composed of parameters, local tags, logic routine, and optional scan mode routines.
safety add-on instruction
An instruction that has a class of safety and is defined as an add-on to the Logix defined instruction set; it is restricted to utilize only safety approved instructions and data types. The logic is currently restricted to RLL.
Class
A read-only field identifying the Class of the instruction, which can be Safety or Standard. The Class field is visible only in a safety controller project.
External Access
Whether the tag has Read/Write, Read Only, or no access (None) from external applications such as HMIs. For more information, see About External Access.
OPC UA Access
Determines the level of access (Read Only, Read/Write, or None) that external OPC UA clients have to tags.
Style
Select the arrow to modify the display style for the Parameter or Local Tag in the Instruction Definition. The Style field appears dimmed if the Data Type is a complex type.
Required
Select so that a check mark appears to specify that the Parameter requires an argument.
The Required field is checked by default for InOut parameters. It is unchecked and appears dimmed for Local Tags.
Visible
Select so that a check mark appears to make this Parameter visible when the Add-On Instruction is called.
The Visible field is unchecked by default for Parameters, but checked if the Required field is checked, and therefore, checked for InOut parameters.
The Visible field is unchecked for Local Tags and appears dimmed.
Constant
Select this check box to prevent executing logic from writing values to the associated tag or parameter. If a logic routine tries to write to a constant tag, the routine will not verify.
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You can use the Data Monitor dialog box to write values to the parameter. The value fields in all other browsers and language editors are disabled when the tag is a Constant tag. Changes made to the values of constant tags will be logged for future reference.
The Constant check box is enabled only if the Usage you selected is the InOut parameter.
Open Configuration
Select so that a check mark appears for the tag configuration dialog box to open when you click the OK button.
This check box is only available for PID data type that are not Local Tags.
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