Rockwell Automation Logix5000 Controllers Add-on Instructions Programming Manual - Manual (Page 37)

Designing Add-On Instructions Chapter 1
Parameters
• What data needs to be passed to the instruction?
• What information needs to be accessible outside of the instruction?
• Do alias parameters need to be defined for data from local tags that needs to
be accessible from outside the Add-On Instruction?
• How does the parameters display? The order of the parameters defines the
appearance of instruction.
• Which parameters should be required or visible?
Naming conventions
The instruction name is to be used as the mnemonic for your instruction.
Although the name can be up to 40 characters long, you typically want to use
shorter, more manageable names.
Source protection
• What type of source protection needs to be defined, if any?
• Who has access to the source key?
• Will you need to manage source protection and an instruction signature?
Source protection can be used to provide read-only access of the Add-On
Instruction or to completely lock or hide the Add-On Instruction and local
tags.
Source protection must be applied prior to generating an instruction
signature.
Nesting - reuse instructions
• Are there other Add-On Instructions that you can reuse?
• Do you need to design your instructions to share common code?
Local tags
• What data is needed for your logic to execute but is not public?
Rock well Automati on Publication 1756- PM010F-EN-P - Oct ober 2014 37