Re: [myhdl-list] my patches

[Jan D. <ja...@ja...>]

On 10/19/2011 04:20 PM, Christopher Felton wrote:

> The constant driver had a good conversation but the conversation
> remained unresolved.  Best I can tell, constant drivers are supported
> in today's MyHDL but not is a form you would like.  The previous
> question of "you disagree with being able to build constant drivers?"
> simply disregarded the previous conversations.

Right. In my view, MyHDL today has a superior solution
called initialization.

Look at it this way. Suppose there would be some kind of "constant
driver" support from some generator. (Actually, the @instance
generator may offer this today, depending on whether the solution
should be synthesizable or not. The suggestion to add this
to @always_comb seems to clash with its semantics to me.)

In that case, how should the Signals in question be initialized?
Remember, the initial value is an explicit part of the Signal
construction, you have to choose one. (This is MyHDL, not Verilog).
It certainly would seem confusing and dubious coding if the
initial value would be different from the "constant driver"
value. Any code reviewer would spot this as an obvious weak point
in the code, and suggest to initialize the Signal to the
"constant" value.

Which proves that the case for special generator support
is without merit, as simply specifying the initial value
is a solution that works today.

> The support for Signals in a class (object) being identified in an
> @always_comb sensitivity list appears to be a good addition.

I agree.

And thanks for a meaningful discussion.

-- 
Jan Decaluwe - Resources bvba - http://www.jandecaluwe.com
     Python as a HDL: http://www.myhdl.org
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