Re: [vhdlsynth] Re: [vhdl-200x-ft] Bit size rules

Jonathan,

Jonathan Bromley wrote:

>PROPOSAL
>~~~~~~~~
>Require that any fixed-point object or subtype have
>a descending array range.
>
>IMPLEMENTATION SUGGESTION (2)
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Modify the base language so that unconstrained
>vector types can be declared to have a range that
>is required to be ascending or descending. I don't
>wish to propose any specific syntax at this point, but
>by way of example you could imagine a construct such
>as this:
>
> type MY_DESCENDING_VECTOR is
> array(integer range <->) of std_logic;
>
> type MY_ASCENDING_VECTOR is
> array(integer range <+>) of std_logic;
>
>Given these type definitions, it would be an error
>(detectable at elaboration time or sometimes earlier)
>to declare a named or anonymous subtype with the wrong
>range direction.
>
>
Could that perhaps be addressed by allowing to set the 'ascending attribute?
No syntax change necessary in that case. Conflicting information
(constrained
range and value assigned to 'ascending don't match) would raise an error.

-- Marcus
Received on Sat Jul 10 11:54:50 2004