RE: suggestion

I don't have any concrete ideas on the syntax, although it does not seem
that difficult to work out, but I don't think you need a time unit
specifier, like 1ns - you would only need to specify the scale factor
(p, n, u) which is already there in the language. The notion of time
(and hence the units, seconds) is already present by virtue of the fact
that you are specifying a delay.

As far as using a variable with a scale factor, you could easily write

#(td * 1n)

or you could even build a unit specifier into the proposed syntax
itself, something like:

#{1n}(td)

In general it is better to be as clear and straightforward as possible,
IMO.

       -- Scott





>>>>-----Original Message-----
>>>>From: Ken Kundert [mailto:ken@designers-guide.com] 
>>>>Sent: Wednesday, August 29, 2007 1:56 PM
>>>>To: Scott Cranston
>>>>Cc: verilog-AMS LRM Committee
>>>>Subject: Re: suggestion
>>>>
>>>>Scott,
>>>>    Would it be keying off the presence of ns? How would 
>>>>this work if I wanted to use a variable? Would I use
>>>>    #(td ns);
>>>>Wouldn't that imply that s, ms, us, ns, ps, fs, etc. would 
>>>>all have to be keywords?
>>>>
>>>>-Ken
>>>>
>>>>Scott Cranston wrote:
>>>>> What you really want is a way to specify time absolutely, correct?
>>>>> 
>>>>> Something like #(1ns) where the 1ns is not scaled.
>>>>> 
>>>>> That seems like a clearer way to do what you want.
>>>>> 
>>>>>    -- Scott
>>>>> 
>>>>> 
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: owner-verilog-ams@eda.org
>>>>>>>>> [mailto:owner-verilog-ams@eda.org] On Behalf Of Ken Kundert
>>>>>>>>> Sent: Tuesday, August 28, 2007 11:44 PM
>>>>>>>>> To: verilog-AMS LRM Committee
>>>>>>>>> Subject: suggestion
>>>>>>>>>
>>>>>>>>> All,
>>>>>>>>>    It would be very handy to have access to the 
>>>>`timescale value 
>>>>>>>>> from within a model so that we can write delays in 
>>>>terms of time 
>>>>>>>>> rather than ticks.
>>>>>>>>>
>>>>>>>>> Just to throw something out, say $tick returns the 
>>>>length of a 
>>>>>>>>> tick in seconds. Then one can use it in the digital 
>>>>portion of the 
>>>>>>>>> model as in the following example (a d flip-flop that 
>>>>implements 
>>>>>>>>> 1n of delay regardless of how `timescale was specified) ...
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> parameter real td = 1ns;
>>>>>>>>> ...
>>>>>>>>>
>>>>>>>>> always @(posedge clk) begin
>>>>>>>>>    q = #(td/$tick) d;
>>>>>>>>> end
>>>>>>>>>
>>>>>>>>> -Ken
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> This message has been scanned for viruses and 
>>>>dangerous content by 
>>>>>>>>> MailScanner, and is believed to be clean.
>>>>>>>>>
>>>>>>>>>
>>>>> 
>>>>

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