Enable Port — Private/Subsystem Components

Enable Port

Control Systems / Ports And Subsystems

Makes the subsystem it sits in an enabled subsystem: the subsystem runs only on the steps its enable signal is strictly greater than zero. Simulink’s Enable block (BlockType=EnablePort). To make one, place this block in a subsystem, or insert the ready-made Enabled Subsystem or Enabled and Triggered Subsystem from the library’s Subsystem Templates.

Ports

• Face – placing it inside a subsystem adds a control input on the top edge of the subsystem block, labelled Enable. The control signal is wired there.
• Output – one, inside the subsystem: the control signal itself, as Simulink’s Show output port gives it. Leaving it unconnected is fine.

Parameters

• States when enabling – held (default) keeps every state across a disabled span; reset returns them to their initial conditions on the step the subsystem is enabled again.

Notes

• A subsystem holds at most one of these. It has to sit inside a subsystem, never at the top level.
• A simulation runs the subsystem only when this port says so; while it does not run, its blocks hold their states and each output port does what its Output when disabled says.

Code export

All ten targets: the subsystem's blocks run under a guard that reads the enable signal, so they execute exactly on the steps it is above zero (any element, for a vector), and each output port holds or resets as its Output when disabled says. States when enabling reset re-seeds the states on the first step the subsystem runs again; on VHDL, Verilog, SystemVerilog and PLC-ST a state the re-seed cannot copy back is refused by name. Also refused by name: an enable driven by a String or bus signal, an enabled subsystem inside an iterated one, and one inside, or holding, a reusable function on every target but Verilog and SystemVerilog.

Simulink bridge

Both directions, as Simulink’s built-in/EnablePort inside the subsystem and the subsystem’s Enable input on its face. States when enabling goes to StatesWhenEnabling, one value for one value. An output wired inside turns on ShowOutputPort, which gives the same signal. The numbered inputs keep their numbers either way.