RE: [sv-bc] configurations and parameters

I agree with Gordon. It might be possible to only allow literal
constants
for value parameters, but with type parameters you would want to be able
to specify user defined types. 

This would have all the same name resolution issues that bind statement
identifiers have. That is not a reason for not doing something like
this. It just means that whatever rules we eventually agree on for bind
will probably have to be used here too. 

> -----Original Message-----
> From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On 
> Behalf Of Gordon Vreugdenhil
> Sent: Thursday, August 09, 2007 11:03 AM
> To: mills@lcdm-eng.com
> Cc: sv-bc@eda.org
> Subject: Re: [sv-bc] configurations and parameters
> 
> Don, your examples all use trivial overrides using literals.
> 
> Would you expect something like the following to work:
> 
>    module top ();
>      parameter WIDTH = 16;
>      adder a1 (...);
>    endmodule
> 
>    config cfgl;
>      design rtlLib.top;
>      instance top.a1 #(.size(WIDTH));
>    endconfig
> 
> It seems to me that such a use model would be required in 
> order to make this viable in practice.  I would expect such 
> scenarios to sort of behave like "bind" in terms of 
> resolution of provided actuals.
> 
> Of course restricting overrides to literals is much simpler 
> but I'm not sure that customers will be happy with that.  
> Allowing fully general constant expression overrides might be 
> difficult and slow implementation, but allowing at least an 
> association to another named parameter should probably be permitted.
> 
> As a second comment, I am not sure that I would agree that a 
> configuration parameter value *always* wins.  In particular, 
> as I mentioned in the meeting, I think that config parameters 
> should be handled as just a replacement instantiation override.
> The implication of this is that a defparam into "top.a1" 
> would win over the configured value.
> 
> Gord.
> 
> Don Mills wrote:
> > As I discussed during the conference on Monday - I would like to 
> > pursue the enhancement of setting parameters via 
> configurations.  The 
> > discussion on Monday noted that there are a number of 
> issues regarding 
> > configurations that need to be addressed, with setting 
> parameters via 
> > configurations being just one of many.  I was tasked 
> (volunteered) to 
> > gather up the issue/wish list regarding configurations and 
> then start 
> > working through it.  Based on the verbal discussion we had on 
> > configurations and the need to have all items resolved by Nov 1 in 
> > order to be part of the next 1800 spec, I see a large task 
> at hand.  I  
> > feel we might have to take small steps - put some of the easier 
> > enhancements in now and add the rest in the next rev.  Of 
> course I am 
> > just speculating at this point.
> > 
> > My enhancement request/proposal for configurations is to add the 
> > ability to set/modify parameters within a configuration.  I have 
> > pieced together some sample code that shows how I think 
> this could work.
> > 
> > // Obviously, parameters set by configurations
> > //   must take precedent over instantiation parameter values.
> > // For this example, I assume that for models from different lib's,
> > //   the port list for each model are (must be?) identical.
> > 
> > module top ();
> >  //See configuration below for details of these instantiations.
> >  adder a1 (...);
> >  adder a2 (...);
> >  adder a3 #(.size(4)) (...);
> >  adder a4 (...);
> >  adder a5 #(.out(16)) (...);
> >  adder a6 #(.out(32)) (...);
> > endmodule // top
> > 
> > //file adder.v, default rtlLib
> > module adder #(parameter size = 12) (...);  // rtl adder  // 
> > description  ...
> > endmodule // adder
> > 
> > 
> > //file adder2.v, in diffRTLLib
> > module adder #(parameter out = 10) (...);
> >  // different rtl adder
> >  // description
> >  ...
> > endmodule // adder
> > 
> > 
> > //file adder.vg, in gateLib
> > module adder (...);
> >  // gate-level adder
> >  // description
> >  ...
> > endmodule // adder
> > 
> > 
> > //This configuration is very verbose for discussion purposes.
> > config cfgl;
> >  design rtlLib.top;
> >  default liblist rtlLIb;
> >  instance top.a2 liblist gateLib;
> > 
> >  //default default lib, override instantiated parameter 
> setting .size(4)
> >  instance top.a3 #(.size(16)); //adder from default liblist
> > 
> >  //different RTLLib, used parameter setting from module,
> >  //not changed by instantiation or configuration
> >  instance top.a4 liblist diffRTLLib; //adder from other 
> than default 
> > liblist
> > 
> >  //different RTLLib, parameter is changed by instantiation but not 
> > configuration  instance top.a5 liblist diffRTLLib; //adder 
> from other 
> > than default liblist
> > 
> >  //different rtl lib, overriding instantiated parameter 
> setting of .out(32)
> >  instance top.a6 #(.out(8)) liblist diffRTLLib; //adder 
> from other than 
> > default liblist
> > 
> > endconfig
> > 
> > 
> > -- 
> > ==========================================================
> > Don Mills
> > mills@lcdm-eng.com
> > www.lcdm-eng.com
> > ==========================================================
> > 
> > 
> 
> -- 
> --------------------------------------------------------------------
> Gordon Vreugdenhil                                503-685-0808
> Model Technology (Mentor Graphics)                gordonv@model.com
> 
> 
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