Rockwell Automation Logix5000 Controllers Add-on Instructions Programming Manual - Manual (Page 41)

Defining Add-On Instructions Chapter 2
4. In the Data Type list, choose the type based on the parameter usage:
• An Input parameter is a passed by value into the Add-On Instruction
and must be a SINT, INT, DINT, REAL, or BOOL data type.
• An Output parameter is a passed by value out of the Add-On
Instruction and must be a SINT, INT, DINT, REAL, or BOOL data
type.
• An InOut parameter is a passed by reference into the Add-On
Instruction and can be any data type including structures and array.
Module reference parameters must be InOut parameters with the
MODULE data type (see Creating a module reference parameter on
page 42 ).
5. If this parameter is intended as an alias for an existing local tag, select the
Alias For check box to select the local tag or its member.
Tip: You can also designate a parameter as an alias for a local tag by using the Tag Editor. See Edit Parameters
and Local Tags on page 45 .
6. In the Default values list, set the default values.
Default values are loaded from the Add-On Instruction definition into the
tag of the Add-On Instruction data type when it is created, and anytime a
new Input or Output parameter is added to the Add-On Instruction.
Tip: If you want to update existing invocations of the instruction to the new default values, select the Copy all
default values of parameters and local tags whose values were modified to all tags of this
instruction type check box at the bottom of the Add-On Instruction Definition Editor. For details on
copying default values, see Copying Parameter or Local Tag Default Values on page 47 .
7. In the Style list, set the display style.
8. In the Req and Vis lists, select the check box to make the parameter
required or visible, as desired.
See Determining Which Parameters to Make Visible or Required on page
32 .
If you decide to make the parameter required, it will also be visible.
9. In the Description list, type a description, maximum 512 characters.
This description appears in the instruction’s help.
10. In the External Access list, select a type for Input or Output parameters;
Read/Write, Read Only, None.
Rock well Automati on Publication 1756- PM010F-EN-P - Oct ober 2014 41