Writing S-Functions

Ada S-Function Specification

The specification specifies the methods that the Ada S-function uses and implements. The specification must specify that the Ada S-function uses the Simulink package, which defines data types and functions that the S-function can use to access the internal data structure (SimStruct) that Simulink uses to store information about the S-function (see SimStruct Functions). The specification and body of the Simulink package reside in the matlabroot/simulink/ada/interface/ directory.

The specification should also specify each callback method that the S-function implements as an Ada procedure exported to C. The following is an example of an Ada S-function specification that meets these requirements.

• -- The Simulink API for Ada S-Function
  with Simulink; use Simulink;
  
  package Times_Two is
  
     -- The S_FUNCTION_NAME has to  be defined as a constant
     -- string.
     --
     S_FUNCTION_NAME : constant String := "times_two";
  
     -- Every S-Function is required to have the
     -- "mdlInitializeSizes" method.
     -- This method needs to be exported as shown below, with the
     -- exported name being "mdlInitializeSizes".
     --
     procedure mdlInitializeSizes(S : in SimStruct);
     pragma Export(C, mdlInitializeSizes, "mdlInitializeSizes");
  
     procedure mdlOutputs(S : in SimStruct; TID : in Integer);
     pragma Export(C, mdlOutputs, "mdlOutputs");
  
  end Times_Two;
  

Ada S-Function Source File Format

Ada S-Function Body