Provides for specification propagation delay and input pulse width, i.e. ‘inertia’ of output:
Inertial delay is default and REJECT is optional :
Output <= NOT Input AFTER 10 ns;
-- Propagation delay and minimum pulse width are 10ns
target <= [REJECT time_expression] INERTIAL waveform;
The keyword INERTIAL may be used in the signal assignment statement to specify an inertial delay, or it may be left out because inertial delay is used by default in VHDL signal assignment statements which contain “after” clauses.
If the optional REJECT construct is not used, the specified delay is then used as both the ‘inertia’ (i.e. minimum input pulse width requirement) and the propagation delay for the signal. Note that in the example above, pulses on Input narrower than 10ns are not observed on Output.