Re: New enable argument to analog events and NULL

Marq is correct; there already is "statement_or_null" for use in events
   @(cross(expr))
      ;

-Geoffrey


Marq Kole wrote:
> Hi Dave,
> 
> I believe the regular BNF is just an empty statement after the vertical 
> bar, so
> 
> analog_expression_or_null ::=
>     analog_expression
>   |
> 
> constant_expression_or_null ::=
>     analog_expression
>   |
> 
> Cheers,
> Marq
> 
> 
> owner-verilog-ams@server.eda.org wrote on 02-04-2008 21:54:27:
> 
>  > The syntax needs to be updated to allow for the new 'enable' argument to
>  > cross/above/timer.
>  >
>  >
>  > analog_event_functions ::= // from A.6.5
>  > cross ( analog_expression [ , analog_expression
>  > [ , constant_expression [ , constant_expression [ ,
>  > analog_expression ] ] ] ] )
>  >
>  >
>  > We are going to allow the user to use NULL arguments for the 
> optionsthey want
>  > to leave as default.
>  > So:
>  > cross(V(a) - 5, , , ,enable) ....
>  >
>  > Here detect crossings in both +ve and -ve direction using simulator 
> default
>  > expressio and time tolerances.
>  >
>  > But the NULL arg is not handled in the analog_expression or
>  > constant_expression
>  > type.
>  > Instead of adding extra [] to the syntax would be better to create 
> anew token:
>  >
>  > analog_expression_or_null ::=
>  >      analog_expression
>  >    | null
>  >
>  > constant_expression_or_null ::=
>  >      analog_expression
>  >    | null
>  >
>  > Cross then becomes:
>  >
>  > cross ( analog_expression [ , analog_expression_or_null
>  > [ , constant_expression_or_null [ , constant_expression_or_null [ ,
>  > analog_expression ] ] ] ] )
>  >
>  > Not quite sure what the convention is in BNF to specify NULL (nill
>  > or prehaps "").
>  >
>  > Dave
>  >
>  >
>  > --
>  > =====================================
>  > -- David Miller
>  > -- Design Technology (Austin)
>  > -- Freescale Semiconductor
>  > -- Ph : 512 996-7377 Fax: x7755
>  > =====================================
>  >
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