Real-Time Workshop

Rapid Prototyping System-Dependent Components

These components contain the program's main function, which controls program timing, creates tasks, installs interrupt handlers, enables data logging, and performs error checking.

The way in which application modules implement these operations depends on the type of computer. This means that, for example, the components used for a DOS-based program perform the same operations, but differ in method of implementation from components designed to run under Tornado on a VME target.

The main Function

The main function in a C program is the point where execution begins. In Real-Time Workshop application programs, the main function must perform certain operations. These operations can be grouped into three categories: initialization, model execution, and program termination.

Initialization

• Initialize special numeric parameters: rtInf, rtMinusInf, and rtNaN. These are variables that the model code can use.
• Call the model registration function to get a pointer to the real-time model. The model registration function has the same name as your model. It is responsible for initializing real-time model fields and any S-functions in your model.
• Initialize the model size information in the real-time model. This is done by calling MdlInitializeSizes.
• Initialize a vector of sample times and offsets (for systems with multiple sample rates). This is done by calling MdlInitializeSampleTimes.
• Get the model ready for execution by calling MdlStart, which initializes states and similar items.
• Set up the timer to control execution of the model.
• Define background tasks and enable data logging, if selected.

Model Execution

• Execute a background task, for example, communicate with the host during external mode simulation or introduce a wait state until the next sample interval.
• Execute model (initiated by interrupt).
• Log data to buffer (if data logging is used).
• Return from interrupt.

Program Termination

• Call a function to terminate the program if it is designed to run for a finite time -- destroy the real-time model data structure, deallocate memory, and write data to a file.

Rapid Prototyping Application Modules
for System Dependent Components

The application modules contained in the system dependent components generally include a main module such as rt_main.c containing the main entry point for C. There may also be additional application modules for such things as I/O support and timer handling.

Rapid Prototyping Program Architecture

Rapid Prototyping System-Independent Components