Case Study

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Hot swap capability on a card, for example, allows the system to determine when a change occurs in the unit's physical configuration, and reallocates the units resources to allow all interfaces to function adequately. This feature allows interfaces on the card to be reconfigured while other interfaces on the router remain unchanged.The software performs the necessary tasks involved in handling the removal and insertion of the card. A hardware interrupt is sent to the software subsystem when a hardware change is detected, and the software reconfigures the system accordingly. When a card is inserted, it is analyzed and initialized in such a way that the end user can configure it properly. The initialization routines used during OIR are the same as those called when the router is powered on. System resources are allocated to the new interface so that it can begin functioning. Likewise, when a card is removed, the resources associated with the empty slot must either be freed or altered to indicate the change in its status.

The failure modes analysis then runs a series of analyses causing the selected components to fail. The fuel economy is monitored during the analysis to see if the system, even after failures occur, continues to perform within specification. The end result is a report giving details of the component failures and the pass/fail state of the fuel economy metric.

To interface the subsystem's generated code with externally written code we must first define the subsystem's input and output signals. We do this by naming the signals in the model, such as pfiltInLeft, and then setting the Real-Time Workshop storage class. There are four storage class settings: