The InOut interface is an important part of the TIA Portal architecture, especially when it comes to Memory Management.
If you aren’t aware of what InOut is, it’s a method by which Functions and Function Blocks are passed information by Reference (or an automatic pointer). When information is passed in this manner, it can be updated immediately, rather than the traditional Input / Output approach that has to wait for the object to complete.
Take a look at the below image and click where InOut interfaces are defined… It’s a dead give away with the double arrow symbol
Every time a Function or Function Block uses an InOut interface, TIA Portal will display the double arrow to show that the data attached is passed both into the block and back out on the same pin.
Why Use InOut?
The memory benefit is much more clear once you start looking at the Offsets in the Declaration view of an object:
This means that we can have hundreds of bytes of information on a single tag, but not have to worry about the memory requirements of housing a copy of them in the instance data of the Function Block.. or the execution time of copying them. This results in a quicker and leaner program.
Drawbacks
With everything there are some drawbacks… What do you think these could be?
The Multiple Choice questions below are designed to test some knowledge around InOut interfaces, their usage and Pointer understanding, as well as how they interact with the wider TIA Portal environment.
This isn’t a test as such, full information as to why something is correct or incorrect is given after 😊
Note: You’ll get +1 point for a correct answer and -1 for an incorrect answer.
Cross-Referencing With InOut Interfaces
Watch the below interactive video, which demonstrates how Cross-Referencing can be misleading when using InOut interfaces, or Pointers.
The below is best viewed in full screen!
If you need a little more help on how to project wide search, a dedicated article exists here:
TIA Portal – Searching Through Entire Project
When trying to follow structured data through interfaces, or across multiple uses in a project, cross-reference doesn’t always work. This…
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