Re: [myhdl-list] Restrictions for conversion

[Christopher F. <chr...@gm...>]

On 5/21/2012 11:58 AM, Jan Decaluwe wrote:
> On 05/21/2012 02:06 PM, Christopher Felton wrote:
>
>> As I write this, I think the rules should be :
>>
>>       1. intbv can have a type None but not the other
>>          Python built-in types: bool, int, long, etc.
>>          (I realize only bool is convertible).
>
> Can you tell me in one sentence why intbv would need this,
> unlike the other types?

To control initial value support, because intbv can be used to model 
memories and the initialization of large internal memories might be 
inefficient and/or unwanted.

This is all in the context of initial value support and extended to 
pre-init RAM (which is possible in an FPGA).

>
> It used to be a like that, and then I kicked it out because
> of too many issues with operators, and lack of a use case.
>
> None is used in TristateSignal to represent high-impedance.
> I don't see another useful use case.
>

What we have been discussing is the API to disable initial value support 
if it was added.  Would it be via additional arguments, special value 
(i.e. None), or a separate type (NoInitSignal?)?

Regards,
Chris