Re: [sv-ac] 1682

Hi Dimitry,

A couple of additional comments on  1682.2007.09.09.pdf.

1) Table 16-25
-------------

I think the example table 16-25 would gain somewhat by adding a row for
a timepoint where the there is an edge on sig in the next timepoint.
I think that would help avoid a possible misunderstanding.
For example at time 40 $sampled(sig)==0, $future_gclk(sig)==0,
$rising_gclk(sig)==false, $falling_gclk(sig)==false,
$changing_gclk(sig)==false, $steady_gclk(sig)==true, (i.e. same as for
time point 30)

2) Example 2
-------------

| Example 2: The following assumptions states that a signal sig must
| remain stable between two falling edges of a clock clk as sampled by
| global clocking. This differs from the property in Example 1 in the case
| where the first falling edge of clk has not yet occurred. In Example 1,
| sig is not allowed to change in that case, but in this example sig can
| toggle freely while we wait for clk to begin.
| 
| a: assume property(@$global_clocking $rising_gclk(clk) ##1
| (!$falling_gclk(clk)[*1:$]) |-> $steady_gclk(sig) );
| 

There seems to be some kind of mismatch between the explanation and the
assumption a.

The property seems to state not that "signal sig must remain stable
between two falling edges of a clock clk" but that sig must be stable
between (and including) any rising edge of clk and (but not
including) the first subsequent falling edge of clk."

Furthermore in case clk has a rising edge before it has its first
falling edge then sig may be constrained before the first falling edge
of clk contrary to what seems to be stated in the explanation.

Best Regards,

Johan M


On Wed, Sep 05, 2007 at 04:33:56PM +0300, Bustan, Doron wrote:
> Hi,
> 
>  
> 
>  
> 
>  
> 
> Here are my remarks
> 
>  
> 
> 1.	Font is not correct.
> 2.	Most of the text should be in blue.
> 3.	first paragraph:
> 
>  
> 
>             I would replace:
> 
>  
> 
>             "These functions include the capability to access the
> previous (resp. the next) value as sampled by 
> 
>              the global clock tick that precedes (resp. follows)
> immediately the time at which the function was called. 
> 
>             Sampling of an expression is explained in 16.4."
> 
>  
> 
>             with
> 
>  
> 
>             "These functions include the capability to access the sample
> value at previous (resp. the next) global clock 
> 
>              tick that precedes (resp. follows) immediately the timestep
> at which the function is called. 
> 
>             Sample value is explained in 16.4."
> 
>  
> 
> 4.	page 1
> 
>             - $falling_gclk(expression) returns true if the sampled
> value of the LSB of the expression
> 
>                 is changing to 1 at the next global clocking tick.
> Otherwise, it returns false.
> 
>  
> 
>     Should be 
> 
>  
> 
>      - $falling_gclk(expression) returns true if the sampled value of
> the LSB of the expression
> 
>         is changing to 0 at the next global clocking tick. Otherwise, it
> returns false.
> 
>  
> 
> 5.	example1, I would say that the error message error("sig is not
> stable"); is executed at time 90.
> 6.	page 3, I would change"
> 
>  
> 
> "The following functions allow to access the immediate past and future
> values as sampled by the
> 
>       global clock or detect changes in values of an expression as
> sampled by the global clock."
> 
>  
> 
>    to
> 
>  
> 
> "The following functions allow to access the sample value of an
> expression at immediate past and future ticks of the
> 
>             global clock and to detect changes in sample value from past
> (current) tick of the global clock to its current (next) tick."
> 
>  
> 
> Doron
> 
>  
> 
>  
> 
> 
> -- 
> This message has been scanned for viruses and
> dangerous content by MailScanner, and is
> believed to be clean.
> 

-- 
------------------------------------------------------------
Johan Mårtensson                 Office: +46 31 7451913
Jasper Design Automation         Mobile: +46 703749681 
Arvid Hedvalls backe 4           Fax: +46 31 7451939
411 33 Gothenburg, Sweden        Skype ID: johanmartensson
------------------------------------------------------------

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