Re: [sv-bc] FW: Proposal for two additional environment parameter functions

I have two small concerns with "$simprobe":
   1)  is the use of the word "parameter".  The example is certainly
       accessing just a normal real variable, not a "parameter".
   2)  it isn't clear whether $simprobe is intended to be a constant
       expression in some cases.  If that is the intent, the rules
       regarding constant expression use should be spelled out.

Gord.


Bresticker, Shalom wrote:
> Hi,
> 
> Please look at this forwarded proposal in the Verilog-AMS committee.
> 
> What interests me in this mail is the general idea of this $simprobe
> function which is used to construct a hierarchical name from string
> constants. I did not examine all the little details.
> 
> What 1800 has is the `` operator within macro definitions.
> 
> The need for a way to construct an identifier name often comes up, and I
> am not sure that `` gives a sufficient solution.
> 
> Note that all the arguments are constants, so that all the work can be
> done at elaboration time.
> 
> Comments?
> 
> Thanks,
> Shalom
> 
> -----Original Message-----
> From: owner-verilog-ams@server.eda.org
> [mailto:owner-verilog-ams@server.eda.org] On Behalf Of David Miller
> Sent: Tuesday, July 10, 2007 5:44 PM
> To: Verilog-AMS LRM Committee
> Subject: Proposal for two additional environment parameter functions
> 
> Hello,
> I would like to propose two new environment parameter functions for LRM
> 2.3
> 
> 1. $freq
> Similar to $abstime, this function will simply return the current
> frequency
> when doing a small-signal analysis.
> 
> [LRM TEXT]
> $freq shall return the current frequency used of a small-signal
> analysis. The
> function shall return zero (0) during DC or transient analysis.
> 
> 
> 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
> 
> Here (assuming that the top level module top is instantiated as "atop")
> module
> grandchild() is asking for the value of 'x' from the instance whose
> hierarchical name is "atop.gc" The above example will print the
> following message:
>    atop.ch.gc: Value of '.atop.ch' is 10.0
> 
> When <instance> is not specified in the hierarchical form, the hierarchy
> will
> be search upwards to find a local instance name that matches. Once the
> instance
>   name has been matched, the value of <param_name> will be retrieved
> from that
> instance. If <param_name> does not exist in the resolved instance, an
> error
> will be raised (or <expression> returned if it has been specified).
> 
> Example:
> module grandchild();
>    parameter string inst = "atop";
>    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
> 
> Here module grandchild() is asking for the value of 'x' from the
> instance whose
>   local name is "atop". The simulator will search up the hierarchy
> looking for
> an instance called "atop". Once it finds "atop" the value of "x" is
> obtained.
> If "atop" does not exist in the hierarchy or did not contain a output
> parameter
> call "x", then an error is raised (or <expression> is returned if
> specfied).
> The above example will print the following message:
>    atop.ch.gc: Value of 'atop' is 5.0
> 
> 

-- 
--------------------------------------------------------------------
Gordon Vreugdenhil                                503-685-0808
Model Technology (Mentor Graphics)                gordonv@model.com


-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.