Data Structures in the Generated Code

The code generator organizes the data used by the model in data structures. For each model, the code generator stores data, such as signals and states, in global structures that are also referred to as standard data structures. Use these data structures to access the data in the generated code.

Real-time model (rtModel) data structure is a top level data structure that contains instance-specific data, which is used by the model for reusable functions. The code generator uses this data structure for only multi-instance code generation.

Standard Data Structures

In a model, root-level Inport and Outport blocks represent the primary inputs and outputs of the block algorithm. By default, the code generator aggregates these blocks into standard structures that store input and output data.

Signal lines, block parameters, states, and other model data appear in the generated code as fields of standard structures. For general information, see How Generated Code Stores Internal Signal, State, and Parameter Data.

The table shows some common data structures in the generated code. The name of the structure type and, if applicable, structure variable in the code that you generate from a model depends on the model settings. Regardless of the settings, the name of the structure type in the code contains the short name from the Short Name of Structure Type column in the table.

Data Structures Generated for a Model

Short Name of Structure Type	Data Represented in the Structure
`ExtU`	Data from root Inport blocks
`ExtY`	Data from root Outport blocks
`B`	Block output signals
`ConstB`	Constant-value block output that could not be inlined
`P`	Block parameters
`ConstP`	Constant-value parameters that could not be inlined
`DW`	Discrete block states
`XDis`	Status of enabled subsystems
`InstP`	Parameter arguments
`SharedDSM`	Shared local data stores

You can exclude data from appearing in these structures by using:

Direct application of storage classes. For example, you can use storage classes to represent signals, tunable parameters, and states as individual global variables. For more information, see C Data Code Interface Configuration for Model Interface Elements.
Configuration parameters, such as those on the Optimization pane in the Configuration Parameters dialog box. You can adjust these configuration parameters to control the default representation of data. For more information, see Model Configuration Parameters: Code Generation Optimization.

Real-Time Model Data Structure

To access the fields of an S-function's simulation data structure (SimStruct), the Simulink^® software provides a set of functions. The code generator replaces SimStruct with an optimized real-time model (rtModel) data structure.

Code generation by using the GRT and ERT system target files uses the real-time model data structure (rtModel). This structure encapsulates model-specific information in a much more compact form than the simulation structure SimStruct. Depending on the model, the model-specific information includes data such as internal data for reusable functions and error state.

When you set the Code interface packaging model configuration parameter to Reusable function, the code generator packages model data (such as block I/O, Dwork, and parameters) into the real-time model data structure. If the model contains blocks that depend on absolute or elapsed time, the code generator packages timer service code into the real-time model data structure regardless of the setting of the Code interface packaging parameter. The code generator passes the real-time model structure by reference to generated model entry-point functions. If you set Pass root-level I/O as (Embedded Coder) to Part of model data structure, the code generator packages root-level model input and output into the real-time model data structure.

Efficient capabilities of the generated code depend on generation of rtModel rather than SimStruct, including:

Integer absolute and elapsed timing services
Independent timers for asynchronous tasks
Generation of improved C API code for signal, state, and parameter monitoring
Pruning the data structure to minimize its size (ERT-derived system target files only)

The real-time model data structure is defined in the main.c or main.cpp file that is generated when you build your model. For ERT models, if you clear the model configuration parameter Generate an example main program (Embedded Coder), rtmodel.h file is generated. The rtmodel.h file contains #include directives required by the rt_main.c or rt_cppclass_main.cpp static main program module. The rt_main.c or rt_cppclass_main.cpp includes rtmodel.h to access model-specific data structures and entry points because the static main program module is not created at code generation time.

The code generator provides a set of macros (C) or methods (C++) for accessing the rtModel data structure. These macros or methods are analogous to the ssSetxxx and ssGetxxx macros that S-functions use to access SimStruct data, including noninlined S-functions compiled by the code generator.

Use the set of macros rtmGetxxx and rtmSetxxx or methods getxxx and getxxx to access the real-time model data structure. These macros or methods are used in the generated code as well as in the main.c or main.cpp module of your external code, respectively. If you are customizing main.c or main.cpp (either a static or a generated file), use rtmGetxxx and rtmSetxxx macros or getxxx and setxxx methods instead of the ssSetxxx and ssGetxxx macros.

Use the rtmGetxxx and rtmSetxxx macros or getxxx and setxxx methods in the same way as you use the ssSetxxx and ssGetxxx versions, except that you replace SimStruct S by real-time model data structure rtM. This table lists rtmGetxxx and rtmSetxxx macros that are used in rt_main.c, and getxxx and setxxx methods that are used in rt_main.cpp. Here, rtm is a pointer to the real-time model data structure.

Macros and Methods for Accessing the Real-Time Model Data Structure

rtm Macro Syntax	rtm Method Syntax	Description
`rtmGetdX(rtm)`	`rtm->getdX()`	Get the derivatives of block continuous states
`rtmGetOffsetTimePtr(rtm)`	`rtm->getOffsetTimePtr()`	Return the pointer to vector that stores sample time offsets of the model associated with rtM
`rtmGetNumSampleTimes(rtm)`	`rtm->getNumSampleTimes()`	Get the number of sample times of a block
`rtmGetPerTaskSampleHitsPtr(rtm)`	`rtm->getPerTaskSampleHitsPtr()`	Return a pointer to `NumSampleTime` × `NumSampleTime` matrix
`rtmGetRTWExtModeInfo(rtm)`	`rtm->getRTWExtModeInfo()`	Return an external mode information data structure of the model (used by code generator only for external mode)
`rtmGetRTWLogInfo(rtm)`	`rtm->getRTWLogInfo()`	Return a data structure used by code generator logging (used by code generator only)
`rtmGetRTWRTModelMethodsInfo(rtm)`	`rtm->getRTWRTModelMethodsInfo()`	Return a data structure of real-time model methods information (used by code generator only)
`rtmGetRTWSolverInfo(rtm)`	`rtm->getRTWSolverInfo()`	Return data structure containing model solver information (used by code generator only)
`rtmGetSampleHitPtr(rtm)`	`rtm->getSampleHitPtr()`	Return a pointer to Sample Hit flag vector
`rtmGetSampleTime(rtm,TID)`	`rtm->getSampleTime(int TID)`	Get task sample time
`rtmGetSampleTimePtr(rtm)`	`rtm->getSampleTimePtr()`	Get pointer to a task sample time
`rtmGetSampleTimeTaskIDPtr(rtm)`	`rtm->getSampleTimeTaskIDPtr()`	Get pointer to a task ID
`rtmGetSimTimeStep(rtm)`	`rtm->getSimTimeStep()`	Return simulation step type ID (`MINOR_TIME_STEP`, `MAJOR_TIME_STEP`)
`rtmGetStepSize(rtm)`	`rtm->getStepSize()`	Return the fundamental step size of the model
`rtmGetT(rtm)`	`rtm->getT()`	Get the current simulation time
`rtmSetT(rtm,t)`	`rtm->setT(time_T t)`	Set the time of the next sample hit
`rtmGetTaskTime(rtm,tid)`	`rtm->getTaskTime(int tid)`	Get the current time for the current task
`rtmGetTFinal(rtm)`	`rtm->getTFinal()`	Get the simulation stop time
`rtmSetTFinal(rtm,finalT)`	`rtm->setTFinal(time_T aTFinal)`	Set the simulation stop time
`rtmGetTimingData(rtm)`	`rtm->getTimingData()`	Return a data structure used by timing engine of the model (used by code generator only)
`rtmGetTPtr(rtm)`	`rtm->getTPtr()`	Return a pointer to the current time
`rtmGetTStart(rtm)`	`rtm->getTStart()`	Get the simulation start time
`rtmIsContinuousTask(rtm)`	`rtm->isContinuousTask()`	Determine whether a task is continuous
`rtmIsMajorTimeStep(rtm)`	`rtm->isMajorTimeStep()`	Determine whether the simulation is in a major step
`rtmIsSampleHit(rtm,tid)`	`rtm->isSampleHit(int tid)`	Determine whether the sample time is hit
`rtmGetErrorStatus(rtm)`	`rtm->getErrorStatus()`	Get the current error status
`rtmSetErrorStatus(rtm,val)`	`rtm->setErrorStatus(const char_T* const aErrorStatus)`	Set the current error status
`rtmGetErrorStatusPointer(rtm)`	`rtm->getErrorStatusPtr()`	Return a pointer to the current error status
`rtmGetStopRequested(rtm)`	`rtm->getStopRequested()`	Return whether a stop is requested
`rtmSetStopRequested(rtm,val)`	`rtm->setStopRequested(int val)`	Set the stop requested flag
`rtmGetBlockIO(rtm)`	`rtm->getBlockIO()`	Get the block I/O data structure
`rtmSetBlockIO(rtm,val)`	`rtm->setBlockIO(B_modelName_T* aBlockIO)`	Set the block I/O data structure
`rtmGetContStates(rtm)`	`rtm->getContStates()`	Get the continuous states data structure
`rtmSetContStates(rtm,val)`	`rtm->setContStates(X_modelName_T* aContStates)`	Set the continuous states data structure
`rtmGetDefaultParam(rtm)`	`rtm->getDefaultParam()`	Get the default parameters data structure
`rtmSetDefaultParam(rtm,val)`	`rtm->setDefaultParam(P_modelName_T* aDefaultParam)`	Set the default parameters data structure
`rtmGetPrevZCSigState(rtm)`	`rtm->getPrevZCSigState()`	Get the previous zero-crossing signal state data structure
`rtmSetPrevZCSigState(rtm,val)`	`rtm->setPrevZCSigState(PrevZCSigStates_modelName_T* aPrevZCSigState)`	Set the previous zero-crossing signal state data structure
`rtmGetRootDWork(rtm)`	`rtm->getRootDWork()`	Get the DWork data structure
`rtmSetRootDWork(rtm,val)`	`rtm->setRootDWork(DW_modelName_T* aRootDWork)`	Set the DWork data structure
`rtmGetU(rtm)`	`rtm->getU()`	Get the root inputs data structure (when root inputs are passed as part of the model data structure)
`rtmSetU(rtm,val)`	`rtm->setU(ExtU_modelName_T* aU)`	Set the root inputs data structure (when root inputs are passed as part of the model data structure)
`rtmGetY(rtm)`	`rtm->getY()`	Get the root outputs data structure (when root outputs are passed as part of the model data structure)
`rtmSetY(rtm,val)`	`rtm->setY(ExtY_modelName_T* aY)`	Set the root outputs data structure (when root outputs are passed as part of the model data structure)

For more information, see S-Function SimStruct Functions.