Real-Time Workshop User's Guide

Simulating Models with Simulink

Before Simulink simulates a model, it orders all of the blocks based upon their topological dependencies. This includes expanding subsystems into the individual blocks they contain and flattening the entire model into a single list. Once this step is complete, each block is executed in order.

The key to this process is the proper ordering of blocks. Any block whose output is directly dependent on its input (i.e., any block with direct feedthrough) cannot execute until the block driving its input has executed.

Some blocks set their outputs based on values acquired in a previous time step or from initial conditions specified as a block parameter. The output of such a block is determined by a value stored in memory, which can be updated independently of its input. During simulation, all necessary computations are performed prior to advancing the variable corresponding to time. In essence, this results in all computations occurring instantaneously (i.e., no computational delay).

Model Execution

Executing Models in Real Time