Re: [myhdl-list] Signal initialization

[Martin T. <mar...@tr...>]

Angel Ezquerra <ang...@gm...> writes:

> I was thinking of the behavior of the code when some signals are still
> not initialized (i.e. undefined). The "stdl" and "bool" functions on
> the pck_myhdl helper file use comparions with 0 and '1'
> (respectively), and I am unsure as to how those will behave when fed
> and undefined value:
>
>     function stdl (arg: integer) return std_logic is
>     begin
>         if arg /= 0 then
>             return '1';
>         else
>             return '0';
>         end if;
>     end function stdl;

You can't feed that an uninitalised value - it takes an integer :)

>
>     function bool (arg: std_logic) return boolean is
>     begin
>         return arg = '1';
>     end function bool;
>

That'll return false for everything other than a '1', so a 'U' (and
'X', and 'Z'...).  Also, 'H' will return false which may or may not be
regarded as a bug?

> In addition I wonder if this will not make VHDL simulations slower
> unnecessarily? I don't know... it just feels a bit unnecessary.
>

I imagine this is a case of correctness-first, performance later (and
only if a proven benefit can be demonstrated)

Cheers,
Martin

-- 
mar...@tr... 
TRW Conekt - Consultancy in Engineering, Knowledge and Technology
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