Formulas

ASCET supports transformation formulas to define the implementation for fixed-point arithmetic. The identity formula is present in each project, other formulas have to be defined in the project editor of the associated project.

The following rules apply:

If the variable has the model data type cont and the implementation data type real32 or real64, only the identity formula should be selected because only this formula is supported by the code generation. If you select another formula, a warning message is displayed in the implementation editor:
Float implementation must have identity formula.
If you do not change the formula, another warning (WIa62) is issued during code generation; the formula is replaced by the identity. See also example 1.
If the variable has the model data type cont and an integer implementation data type, the identity or a linear formula can be used in all circumstances.
Non-linear formulas are allowed in certain cases. Therefore, no error or warning message is displayed in the implementation editor.
- non-linear formulas in general:
  - an assignment if the left side and the right side use identical formulas
- reciprocal formulas:
  - division of a value with linear formula by a value with reciprocal formula
  - division of two values with reciprocal formulas
  - multiplication of a value with reciprocal formula and a value with linear formula (result has a linear formula)
  - assignment of a value with reciprocal formula to a value with linear formula
  - assignment of a value with linear formula to a value with reciprocal formula
  - assignment of a literal value to a value with reciprocal formula
- If all operands are literal values or values with identical reciprocal formula AND if the value ranges of all operands are strictly positive or strictly negative, the following operations can be used:
In other cases, an error MMdl623 is issued during code generation.
See also example 2.
If you edit an element with model data type limitInt, wrapInt, sdisc or udisc, and select another formula than the identity, an error message is displayed in the implementation editor:
Disc model type must have identity formula.
You must correct the formula (e.g., with the Auto Correction button in the implementation editor) or cancel the implementation.
Note
Models from earlier ASCET versions can be used unchanged. During code generation, however, warnings are generated if they contain formulas for discrete elements.

Note
Models from earlier ASCET versions can be used unchanged. During code generation, however, warnings are generated if they contain formulas for discrete elements.

If you make changes in a formula, or recursively replace a formula in a project implementation, you can have all your implementations updated automatically to match the new value ranges and data types. For information on replacing formulas and updating implementations see Global Changes in Implementations.