Get the offset from the start of the bus data type to a bus element


int_T ssGetBusElementOffset(SimStruct* S, int_T busTypeID, int_T elemIdx)



SimStruct that represents an S-Function block


The bus data type identifier that represents the bus signal


The zero-based bus element index




Use to get the offset, in bytes, from the start of the bus data type to the bus element that you specify and to obtain a pointer to the memory location of the bus element. The ssGetBusElementOffset S-function accounts for the data type, complexity, dimensions, and any padding between the start of the bus signal and the bus element that you specify.

Bus S-function Usage Guidelines

Use this S-function in simulations. You cannot use this S-function for code generation.

This S-function does not support bus elements that have any of the following characteristics:

  • Variable dimensions

  • Frames

  • Enumerated (enum) data types

To use this S-function and other bus-related S-functions, before you run the simulation, execute the following MATLAB® command:

set_param(block_handle, 'EnableBusSupport', 'on')

To automate setting the EnableBusSupport parameter, use one of the following approaches:

  • Add the command to the model initialization callback.

  • Mask the S-Function block and add the command to the mask initialization callback


C, C++


static void mdlOutputs(SimStruct *S, int_T tid)
    DTypeId    dType    = ssGetOutputPortDataType(S, 0);
    const void *u       = ssGetInputPortSignal(S, 0);
    int        numElems = ssGetNumBusElements(S, dType);
    int        i;
    for(i=0; i<numElems; i++) {
        int_T offset = ssGetBusElementOffset(S, dType, i);
        /* Assume that the bus element is of type double */
        const double *in = (const double*) ((const char*)u + offset);

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