Re: [myhdl-list] Reset functionality "synthesis"

[Tom D. <td...@di...>]

On 07/03/2012 01:45 PM, Jan Decaluwe wrote:
> On 07/03/2012 06:40 PM, Angel Ezquerra wrote:
>
>> Jan,
>>
>> given how contentious the asynchronous vs synchronous reset debate is
>> I would argue that there should be no default value in this case, and
>> that the reset type should always be set explicitly.
> I am quite surprized by this, is this really so contentious?
> In my whole career as a design engineer, I don't recall one
> single incident about this (many about other issues :-)).
>
> Actually, I have *always* used the mixed approach, where you
> go into reset asynchronously, but come out of it synchronously.
> In this method, the reset driver comes out of a ff that
> is reset asychronously with the primary reset, and that
> also synchronizes the primary reset.
>
> For this to work, the ffs in the design should have
> an asynchronous reset, but that doesn't mean the
> reset scheme itself is asynchronous, as described.
> The big advantage of this method is that you don't
> need the clock to be present to go into reset,
> only to come out of it. So you avoid power-up issues
> with clocks and pll's.
>
> I thought this was the standard practice, which is why
> I intuitively made it the default.
>
> I'd like to hear more opinions.

I would prefer to have a default value and would vote for async.


>