Writing S-Functions

Creating Output Ports

To create and configure output ports, the mdlInitializeSizes method should first specify the number of input ports that the S-function has, using ssSetNumOutputPorts. Then, for each output port, the method should specify:

• Dimensions of the output port

• Simulink provides the following macros for setting the port's dimensions.
  • ssSetOutputPortDimensionInfo
  • ssSetOutputPortMatrixDimensions
  • ssSetOutputPortVectorDimensions
  • ssSetOutputWidth

  If you want the port's dimensions to depend on block connectivity, set the dimensions to DYNAMICALLY_SIZED. The S-function must then provide mdlSetOutputPortDimensionInfo and ssSetDefaultPortDimensionInfo methods to ensure that output port dimensions are set to the correct values in code generation.

• Data type of the output port

• Use ssSetOutputPortDataType to set the output port's data type. If you want the data type of the port to depend on block connectivity, specify the data type as DYNAMICALLY_TYPED. In this case, you must provide implementations of the mdlSetOutputPortDataType and mdlSetDefaultPortDataTypes methods to enable the data type to be set correctly during signal propagation.

• The numeric type of the input port, if the port outputs complex-valued signals

• Use ssSetOutputComplexSignal to set the output port's numeric type. If you want the numeric type of the port to depend on the numeric type of the port to which it is connected, specify the data type as inherited. In this case, you must provide implementations of the mdlSetOutputPortComplexSignal and mdlSetDefaultPortComplexSignal methods to enable the numeric type to be set correctly during signal propagation.

Creating Input and Output Ports

Scalar Expansion of Inputs