Highlighting safe logic in the FBD-editor

The FBD-editor highlights safe logic with shades of yellow so you can visually distinguish safe logic from non-safe logic when developing safety-related applications.

logi.cals recommends that you and/or your system integrator do not use yellow shades when designing FBD-elements because the color "Yellow" is used for tracking safe signals when developing safety-related applications. logi.CAD 3 does not check if colors are already used elsewhere. So the use of the yellow shades by you and/or your system integrator could have the consequence that "yellow" might also identify a non-safe logic as well.

The following FBD elements are displayed with shades of yellow:

• →value fields, provided that the value field contains a →variable that is declared based of a safe data type or provided that the value field contains a →literal and it is connected to another FBD-element that is displayed with shades of yellow.
  

• the →call of a →function or of a →function block, provided that it is a block for safe logic and that a safe value is delivered to this block according to the details under "Blocks for safe logic".

• lines that are connected to such value fields/calls

• →connectors and →continuations for such lines

This logic is a non-safe logic because the data type INT is used:

Here is the same logic but with the safe data type SAFEINT - which causes the elements to be displayed with shades of yellow to indicate the safe logic:

You can also mix safe logic and non-safe logic. The implicit conversion of a safe data type to a non-safe data type is allowed.

Illegal constructs will be highlighted as errors or warnings in the FBD-editor. Since the implicit conversion of a non-safe data type to a safe data type is an illegal construct, the assignment of the ADD output to the safe variable resultB is highlighted as faulty in the above example. Reason: The inputs of the ADD block are connected to non-safe variables.
Workaround: Call the respective safe-convert function , for the above example this is the TO_SAFEINT block: