Subject: [vhdl-200x-mp] Re: Bi-directional signals and resistors
From: Kevin Cameron (Kevin.Cameron@nsc.com)
Date: Mon May 05 2003 - 10:12:15 PDT
Another interesting device to model is a capacitor - can you do a simple
model that will hold the value on a net for a while after other drivers have
gone to Z/null? (it's a single ported component).
Kev.
Jim Lewis wrote:
> The resistor seems to be the interesting part.
> If the bidirectional assignment operator were
> like a "port mapping" then perhaps resistors
> could be handled similar to handling type
> conversions in a port map.
>
> Basic bidirectional assignment:
> A <=> B ;
>
> Extended to allow resistors:
> to_WLH(A) <=> to_WLH(B) ;
>
> where the to_WLH function is similar to to_X01 except
> it maps 0 and L to L, 1 and H to H, and all others
> to W.
>
> Cheers,
> Jim
>
>
> Jim Lewis wrote:
>
>> Hi Rick,
>> You sound a little frustrated. We have an issue
>> list based on the DVCon documents (posted on
>> vhdl-200x home page). This issue is already
>> on the list.
>>
>> > What else should I do to promote my cause?
>> Perhaps flush out some detail of what you envision
>> for the implementation.
>>
>> For example, when I first started thinking of this
>> I thought of a bidirectional operator that
>> attaches two bidirectional ports:
>>
>> A <=> B ;
>>
>> However, David Bishop showed me some interesting
>> things he would like to be able to do for pass-gate
>> multiplexers:
>>
>> bidir_mux : process (Sel, A, B, C)
>> begin
>> case sel is
>> when "00" => A <=> B ;
>> when "01" => A <=> C ;
>> when "10" => B <=> C ;
>> when others =>
>> end case ;
>> end process ;
>>
>>
>> If we do this, do we need to be able to do
>> concurrent assignments:
>> A <=> B when S = '1' else C ;
>>
>>
>> Do we allow the following or do the expressions
>> have to resolve to signals?
>> A <=> B and C ;
>>
>>
>> Your request includes, switches, resistors, and
>> transmission gates. I think the above may address
>> switches and transmission gates, how do we do resistors?
>>
>> At minimum the above needs to be made some sense
>> of an integrated into the MP-001 proposal.
>>
>> Cheers,
>> Jim
>>
>>
>>
>>
>>
>> Munden Rick wrote:
>>
>>> Jim,
>>>
>>> OK, I have submitted the proposal (for the third time). What else
>>> should I do to promote my cause?
>>>
>>> Rick
>>>
>>> Jim Lewis wrote:
>>>
>>>> Bidirectional assignment is on the list.
>>>> It is a matter of formalizing the request, submitting
>>>> an analysis, voting, and resolving the issue.
>>>>
>>>> We need a volunteer or two to address this issue.
>>>> Anyone interested in volunteering? (hint)
>>>>
>>>> This is issue MP-001. The proposal template is at:
>>>>
>>>> http://www.eda-twiki.org/vhdl-200x/proposals/proposal_template.txt
>>>>
>>>> Cheers,
>>>> Jim
>>>>
>>>>
>>>>
>>>> Steve Casselman wrote:
>>>>
>>>>> Verilog has many constructs like this. It allows Verilog to model
>>>>> almost
>>>>> anything you need to model and design an ASIC. I believe that
>>>>> Verilog is the
>>>>> language most ASIC designers use because of this (and performance
>>>>> issues).
>>>>> What would it take to have VHDL cover the same turff as Verilog in
>>>>> this
>>>>> respect?
>>>>>
>>>>> Steve
>>>>> ----- Original Message ----- From: "Kevin Cameron x3251"
>>>>> <Kevin.Cameron@nsc.com>
>>>>> To: <vhdl-200x-mp@server.eda.org>
>>>>> Sent: Wednesday, April 30, 2003 9:56 AM
>>>>> Subject: [vhdl-200x-mp] Re: Bi-directional signal flow
>>>>>
>>>>>
>>>>>
>>>>>>> From owner-vhdl-200x-dta@eda.org Wed Apr 30 06:50:10 2003
>>>>>>>
>>>>>>> Kevin,
>>>>>>>
>>>>>>>
>>>>>>>> Is this the right group for tackling bi-directional signal flow
>>>>>>>> (for
>>>>>>>> modeling transmission gates etc.)?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> No, I'd say that the right group is Modeling and Productivity
>>>>>>> (vhdl-200x-mp).
>>>>>>>
>>>>>>> Paul
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> A friend of mine has been bugging me for a while to fix this
>>>>>> aspect of
>>>>>> VHDL for him, is anyone else interested?
>>>>>>
>>>>>> The extensions would allow users to create digital models for
>>>>>> transmission
>>>>>> gates and other bi-directional devices.
>>>>>>
>>>>>> Kev.
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
>
>
>
>
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