Contents Up << >>
Selected signal assignment
The selected signal assignment is a better way to model a multiplexer and
is like the case statement in typical programming languages. The syntax
follows the rule:
The expression is used to select one waveform to apply to the projected
waveform. The choices specify for what values of the expression its
corresponding waveform should be chosen. Like the conditional waveforms,
the choices are checked sequentially from first to last. The waveform
corresponding to the first set of choices that match the value of the
expression is
applied to the projected waveform. Only one waveform is chosen. All of
the choices in a selected signal assignment taken together must cover all
possible values of the expression. If, at the time of execution, the
expression
is evaluated and none of the choices match, then the execution is stopped with
an error message.
The OTHERS choice will match any value of the expression.