RE: Analog function question

Hi, Marq.

 

Regarding defparams, you are correct that it has fallen in disfavor.

Personally, I think the community has exaggerated in its disfavor.

Like any other construct, you need to use it wisely.

I think it is possible to have lint tools check for unsafe uses.

I realize I may be in a small minority here, but I think I represent a
large group of responsible users which is simply not well represented on
this point in the standards committees.

 

However, I think the statement that defparam is not widely supported by
simulators is not correct.

I don't know of any significant digital Verilog simulator which does not
support it.

 

Regarding #2, I meant something like the following. I'll use a digital
Verilog example.

 

module qq;

parameter N = 3;

parameter M = 5;

parameter P=2;

 

function [N:1] gg (input [M:1] ii);

reg[P:1] aa ;

...

endfunction

 

 

module top;

gg #(.N(2),.M(7),.P(1)) gg(7'd33);

...

endmodule

 

 

Shalom

 

 

________________________________

From: owner-verilog-ams@eda.org [mailto:owner-verilog-ams@eda.org] On
Behalf Of Marq Kole
Sent: Monday, September 19, 2005 11:05 AM
To: verilog-ams
Subject: RE: Analog function question

 


Shalom, 

> Re the statement that "you cannot set a parameter value (of a 
> function) from the outside", 
> I think there are 2 ways that you CAN do it: 
>   
> 1. defparam 

You're right, but I think defparam has fallen in disfavor with 
at least the SV community and it is not widely supported by 
simulators. 

> 2. Use a parameter which is defined in the module enclosing the 
> function. That parameter value CAN be overridden. 

But then it is not longer the same parameter anymore, it is just 
a local parameter which happens to share the same name. Per 4.6.1 
it can only reference local variables or variables passed in as 
arguments; the whole paragraph does not mention parameters 
anywhere. 

Or, is this what you mean: 

module test_me (a, b); 
parameter integer n = 2 from [0:inf); 
inout[0:n-1] a, b; 
electrical[0:n-1] a, b; 

  analog function integer some_array_manip; 
  parameter integer n = n; 
  inout[0:n-1] a; 

  ... 

  endfunction 

  ... 

endmodule 

The reference to parameters of the enclosing module is not mentioned 
in 4.6 explicitly, but the above looks acceptable to me. 

I stand corrected :-) 

Regards, 
Marq 


>   
> Shalom 
>   
>   
> 
> From: owner-verilog-ams@eda.org [mailto:owner-verilog-ams@eda.org] 
> On Behalf Of Marq Kole
> Sent: Friday, September 16, 2005 10:28 AM
> To: verilog-ams
> Subject: Re: Analog function question 
>   
> 
> Oops, need to correct a small mistake below: 
> 
> > Sri, Arpad, 
> > 
> > > In strict accordance to the BNF it cant be done yet. I think it
was 
> > > an oversight/bug in the BNF and the intent was to put it in there.
> > 
> > In accordance with the BNF, the input declaration is mentioned as a 
> > digital_input_declaration in Annex A, so its actual definition is in
the 
> > IEEE 1394-1995 standard. See Mantis item #870. 
> > 
> > For array arguments see Mantis item #869 describing the problem - it
is 
> > rather an issue of documentation (explanation + example) than a
missing 
> > item in the standard. 
> > 
> > > 
> > > regards,
> > > Sri
> > > 
> > > Muranyi, Arpad wrote: 
> > > Sri,
> > > 
> > > I just saw your 2nd reply, but since I had this almost finished,
> > > I will send it out anyway...  So according to your 2nd message,
> > > this can't be done (yet)?
> > > ----------------------------
> > > Thanks for the quick answer.  Sorry, but I am still not sure
> > > about it.  The sections you quoted from the LRM seem to allow
> > > the array inside the function as a block item, but I still
> > > don't see how I can pass an array into the function (and
> > > pass it as a real variable array, not as a parameter array).
> > 
> > Parameter arrays in functions wouldn't help you anyway, as you 
> > cannot set them from outside the function, and once initialized, 
> > you cannot alter them from inside the function either. 
> >  
> > > Would you be so kind and help me with an example?  If the
> > > input "in1" is an array, how would you declare it in the
> > > function?
> > > 
> > > analog function real myFunctionName;
> > > input in1;
> > > real  in1[1:5];    <--------- How would I know the size?
> > 
> > You'd know the size as the above analog function declaration tells 
> > you the size. There is at this moment no way to make an array
argument 
> > with parameter-controlled size in an analog function in Verilog-AMS
-- 
> 
> I mean an argument-controlled size given the fact that you cannot set 
> a parameter value from the outside. So a call: 
> 
>   myArrayFunction(myArraySize, myArray); 
> 
> Where myArraySize argument carries the length of the myArray argument 
> cannot be handled in current Verilog-AMS. 
> 
> > we need to check what System-Verilog does to resolve that for a
future 
> > LRM, I think. 
> > 
> > > begin
> > > ...
> > > ...
> > > end
> > > endfunction
> > > 
> > > 
> > > Thanks,
> > > 
> > > Arpad
> > 
> > Marq Kole
> > Competence Leader Analog Simulation, Philips ED&T