Re: Proposal for two additional environment parameter functions

Hi Bob,
I think I was misleading before, sorry. I mean I currently have $simprobe() 
implemented in my simulator as an extension. It needs to actually get values 
from the simulation engine, I have to access values and functions that are not 
accessible to users. So even if I implement it as a VPI function, doesn't it 
mean that I still internally need code that knows how to get the values from my 
simulator engine? And if another simulator tried to use a model that contained 
$simprobe, wouldn't it also need its own specific code to extract the values? 
What am I missing?

As for $simparam, my first thought was to merge $simparam into $simprobe where 
if the first argument to $simprobe was a empty string, the behaviour would be 
the same as $simparam

$simprobe("","gmin") == $simparam("gmin")

But unfortunately this won't work as $simparam is already out there. $simprobe 
does a lot more than $simparam, so I don't think it would be able to be merged 
into $simparam cleanly. Plus the name of $simparam is misleading, $simprobe, is 
not accessing parameter values, it is accessing dynamic device quantities 
during simulation.

Cheers...
Dave

Bob Floyd wrote:
> Hi Dave,
> 
> A. Can you explain why your current VPI implementation of `$simprobe` is
> non-portable?
> 
> B. Why not improve `$simparam` to support the proposed new features of
> `$simprobe`?
> 
> Bob
> 
>> -----Original Message-----
>> From: David Miller [mailto:David.L.Miller@freescale.com]
>> Sent: Wednesday, July 11, 2007 4:53 AM
>> To: Bob Floyd
>> Cc: verilog-ams@eda.org
>> Subject: Re: Proposal for two additional environment parameter functions
>>
>>
>> Hi Bob,
>> That is how I currently do it, but it means that models that we
>> implement using
>> this feature are non-portable which I want to avoid. I was
>> thinking that this
>> function is useful enough that it can be part of the language.
>> Note that although the examples I show are Verilog-AMS, the main
>> need for this
>> function is to retrieve values from spice primitive and sub
>> circuit devices. We
>> currently have no way in the language to get values from the
>> Spice engine apart
>> from $simparam() which is too limited.
>>
>> Cheers...
>> Dave
>>
>> Bob Floyd wrote:
>>> Why not implement $simprobe as your own VPI function, thus minimizing
>>> clutter in the language?
>>>
>>> -------------------------------------------
>>> 2. $simprobe(instance, param_name [, expression])
>>> Similar to $simparam(), this function will retrieve the value
>> of a given
>>> parameter from a given instance. If the instance/parameter does
>>> not exist, it
>>> will stop with an error. If the optional argument <expression> is
>>> specified, it
>>> will return this value in lieu of the error. This function is not
>>> limited to
>>> retrieving values from Spice elements, but also Verilog-AMS instances.
>>>
>>> [LRM TEXT]
>>> $simprobe() allows the user to query the value of an element within the
>>> specified instance. The function returns a real scalar value.
>>> The general form of the $simprobe function is:
>>> 	$simprobe(instance, param_name [, expression])
>>>
>>> <instance> is a string constant (either a literal or string
>>> parameter). If the
>>> string is prefixed with a '.' character, then the characters
>>> following the '.'
>>> character make up the full hierarchical name of the instance to
>>> query. If the
>>> first character of the instance string is not a '.', then the
>>> string is the
>>> local name of the instance to query. It is a compilation error to use a
>>> hierarchical instance name where the string is not prefixed with
>>> a '.' character.
>>>
>>> <param_name> is the name of the parameter whose value is
>> required. It is a
>>> string constant (either a literal or string parameter). A
>>> parameter can be any
>>> valid scalar or indexed vector output parameter for the instance
>>> in question.
>>>
>>> <expression> is an optional argument. It can be any valid Verilog-AMS
>>> expression. When specified, its value will be returned in case of
>>> an error.
>>>
>>> When <instance> is specified in the hierarchical form,
>>> <param_name> will be
>>> retrieved from <instance>. If <instance> or <param_name> does
>> not exist an
>>> error will be raised. If <expression> has been specified, it's
>>> value will be
>>> returned in lieu of raising the error.
>>>
>>> Example:
>>> module grandchild();
>>>    parameter string inst = ".atop.ch";
>>>    analog $strobe("%m: Value of '%s' is %g", inst, $simprobe(inst,"x"));
>>> endmodule
>>> module child();
>>>    real x;
>>>    grandchild gc();
>>>    analog x = 10;
>>> endmodule
>>> module top();
>>>    real x;
>>>    child ch();
>>>    analog x = 5.0;
>>> endmodule
>>>
>>>
>>>
>>>
>> --
>> =====================================
>> -- David Miller
>> -- Design Technology (Austin)
>> -- Freescale Semiconductor
>> -- Ph : 512 996-7377 Fax: x7755
>> =====================================
> 
> 

-- 
=====================================
-- David Miller
-- Design Technology (Austin)
-- Freescale Semiconductor
-- Ph : 512 996-7377 Fax: x7755
=====================================

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