RE: suggestion

My opinion is that the notion of the "absoluteness" of the delay should
be present in the delay specification itself. Otherwise you have to look
back to the definition of the variable to determine this - which leads
to confusion.
 
      -- Scott
 


________________________________

	From: Kevin Cameron [mailto:dkc@grfx.com] 
	Sent: Thursday, August 30, 2007 1:33 AM
	To: Scott Cranston
	Cc: Ken Kundert; verilog-AMS LRM Committee
	Subject: Re: suggestion
	
	

	Maybe you want a new type (say) realtime e.g.:
	
	  realtime td = 1.2345ns;
	
	  # td;          // as near a 1.2345ns delay as poss.
	
	Kev.
	
	Scott Cranston wrote: 

		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
				
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