RE: [sv-bc] configurations and parameters

Hi,
Few issues/suggestions

1. In the example from Gord, where WIDTH is set as parameter from 
configuration, scope resolving can get very complicated. I would
suggest against introducing such changes in SV.
   We should rather have parameter/localparam declarations inside
configurations which can be used for overriding instance parameters.
This will not work like binding and cannot handle Gord's case.

2. For overriding parameters inside configuration, instead of
introducing a new Syntax, with it's precedence complexity, we
can think of using defparam inside configuration.
  
Slightly modified version of Don's example with my suggestions:
module top ();
  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;

  // SUGGESTION
  localparam WIDTH = 8;

  //using default lib, override instantiated parameter setting .size(4)
  // SUGGESTION
  defparam top.a3.size = WIDTH*2; //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 liblist diffRTLLib; //adder from other than default
liblist

  //parameter specified separately from instance library binding.
  defparam top.a6.out = 8;

endconfig

Thank you,
Saikat


-----Original Message-----
From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of Gordon
Vreugdenhil
Sent: Thursday, August 09, 2007 11:33 PM
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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