RE: Port directions

Hi,

I think:

The port directions are used to identify the direction where the "information" is going to. A branch with input on both sides would mean that this is an "information" sink. (input a,b;)

How the current is flowing through the branch is irrelevant regarding "information" direction, but relevant in physical/electrical simulations (electrical a,b;).

Potential examples:

Electrical feed through:
Inout a,b;
electrical a,b;

Current controlled voltage source
Input a,b;
electrical a,b;

I think input, output, inout is independent relative to (some) disciplines.

Kurt

Kurt Neugebauer
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-----Original Message-----
From: owner-verilog-ams@eda.org [mailto:owner-verilog-ams@eda.org] On Behalf Of Kevin Cameron
Sent: Friday, June 04, 2010 9:20 AM
To: Ken Kundert
Cc: Marq Kole; Verilog-AMS LRM Committee
Subject: Re: Port directions

From a circuit designers perspective source/sink is an aspect of function not current sign. E.g. on accelerometer circuits we had at Ferranti there were constant-current sinks used as dummy loads, I don't think input/output has any meaning in that context.

Kev.

On 06/04/2010 12:05 AM, Ken Kundert wrote:
> It would be an input if you are sensing the current, and an output if
> you are driving the current. Sourcing or sinking is just an issue of
> the sign of the current.
>
> -Ken
>
> On 06/03/2010 11:40 PM, Kevin Cameron wrote:
>
>> I don't think that's sufficient - is a constant current a source or a
>> sink, input or output?
>>
>> The input/output stuff makes sense at some levels of abstraction, but
>> not when you're talking about which way currents are going. You would
>> also have to consider the interaction with sub-modules, OOMRs and
>> back-annotation.
>>
>> I think any attempt interpret input/output usage as an error will
>> just cause problems. I voted "no" on this one when it came up for
>> Verilog-A 1.0, I'm still voting "no".
>>
>> I would suggest talking to your vendor(s) and getting it added as an
>> option to see how it works in practice before committing anything to
>> the LRM.
>>
>> Kev.
>>
>> On 06/03/2010 05:49 PM, Ken Kundert wrote:
>>
>>> Marq,
>>> It seems to me that with signal flow the port direction can be
>>> checked to assure that it consistent with the behavior.
>>>
>>> Kevin,
>>> Signal flow is easily recognized by the fact that the
>>> disciplines have only one nature.
>>>
>>> -Ken
>>>
>>> On 06/03/2010 05:26 PM, Kevin Cameron wrote:
>>>
>>>
>>>> How are you going to recognize signal flow?
>>>>
>>>> You might want to try addressing this issue in the assertions
>>>> committee
>>>> - i.e. if you can make up some rule about
>>>> drivers/contributions/disciplines that can be tested then this
>>>> problem moves into user space (being programmable) rather than
>>>> being hard-defined in the standard.
>>>>
>>>> Kev.
>>>>
>>>> On 06/03/2010 02:26 AM, Marq Kole wrote:
>>>>
>>>>
>>>>> Hi Kevin, Ken,
>>>>>
>>>>> I can understand not wanting to impose this limitation for conservative disciplines, but how about signal-flow disciplines? There you want to make sure that not more than one driver exists for a potential-only discipline or more than one sink for a flow-only discipline.
>>>>>
>>>>> Cheers,
>>>>> Marq
>>>>>
>>>>> -----Original Message-----
>>>>> From: owner-verilog-ams@eda.org [mailto:owner-verilog-ams@eda.org]
>>>>> On Behalf Of David Miller
>>>>> Sent: Wednesday 2 June 2010 21:01
>>>>> To: Verilog-AMS LRM Committee
>>>>> Subject: Port directions
>>>>>
>>>>> Should the language enforce that port directions are honored?
>>>>> Specifically ports that are defined as input, should it be a error
>>>>> if you contribute to a branch containing that port?
>>>>>
>>>>> module mymod(a,b);
>>>>> electrical a,b;
>>>>> input a,b;
>>>>> analog V(a,b) <+ 5;
>>>>> endmodule
>>>>>
>>>>> Should this be an error, since a,b are input?
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>

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