ABSTRACT

Among the many features o f Simulink that the user needs to understand, perhaps none is more powerful than the "Enabled" and "Triggered" subsystem feature. Within the Simulink connections block set are two blocks that really are not blocks at all, but are behavior modifiers. The first o f these, the Enabled block, causes a subsystem to be turned on or o f f based on a signal. When the enable block is placed in a subsystem, an enable input appears on the subsystem block whenever the value o f the input at this port is greater than zero. The block itself can be used to specify what happens to the internal subsystem states when the enable signal goes away (i.e. are the states held at their last value or are they re­ set?). A triggered subsystem w i l l be executed once when a trigger signal appears at the input port. The trigger may be set to be rising, falling, or both. Triggered subsys-

terns must always be discrete. The subsystems that are not enabled are not exe­ cuted when the Simulink simulation is started. Since they are only executed when the enable signal is greater than zero, there is no penalty in the simulation speed.