RE: [sv-bc] Query about '1

worse case with parameter is like below '1 used on parameter assignment list
- but it still should return all ones?
module top;
        sub #('1) uut();
        initial uut.r1='1;
endmodule
 
module sub;
 
parameter [63:0] p1 = 0;
reg [63:0] r1 = 0;
initial begin #0
    $display( "%b",p1);
        $display( "%b",r1);
end
 
endmodule


  _____  

From: owner-sv-bc@server.eda.org [mailto:owner-sv-bc@server.eda.org] On
Behalf Of Bresticker, Shalom
Sent: 8 lipca 2008 16:13
To: Surya Pratik Saha
Cc: Banerjee, Ayan; sv-bc@server.eda-stds.org
Subject: RE: [sv-bc] Query about '1


Hi,
 
One can make a case for claiming that `1 should be evaluated as
self-determined as a port connection, but not using your argument.
 
It is true that simulators give port connection size mismatch warnings. But
the LRM does not require them to do so. The LRM does explicitly say that
port connections are modeled as continuous assignments (unless port
collapsing is performed). In contrast to regular continuous assignments
where size-mismatching is frequently deliberately done, it is relatively
rarely deliberately done on port connections and thus more likely to be an
error.
 
Regards,
Shalom


  _____  

From: Surya Pratik Saha [mailto:spsaha@cal.interrasystems.com] 
Sent: Tuesday, July 08, 2008 5:05 PM
To: Bresticker, Shalom
Cc: Banerjee, Ayan; sv-bc@eda-stds.org
Subject: Re: [sv-bc] Query about '1


Hi Shalom,
I have some comment on e.g. <1> answer. Conceptually your answer is correct.
But the answer should be <c>. Because at the time of port connection, the
actual expression should be evaluated in context insensitive manner.
Consider the following e.g:
module top;
    wire [2:0] x;
    test t(x);
endmodule
module test(i);
    input [3:0] i;
endmodule

All standard simulators gives port connection size mismatch warning as per
LRM. If the port connection is simple continuous assignment then there is no
need to give that warning. Considering that, if '1 is evaluated in context
insensitive manner, then as per SV LRM, the value will simple one bit 1.
Hence the answer should be <c>.

Regards

Surya


-------- Original Message  --------
Subject: Re:[sv-bc] Query about '1
From: Bresticker, Shalom  <mailto:shalom.bresticker@intel.com>
<shalom.bresticker@intel.com>
To: Banerjee, Ayan  <mailto:ayan_banerjee@mentor.com>
<ayan_banerjee@mentor.com>, sv-bc@eda-stds.org
Date: Tuesday, July 08, 2008 7:09:33 PM


I think the answers should be:


  _____  

From: owner-sv-bc@server.eda.org [mailto:owner-sv-bc@server.eda.org] On
Behalf Of Banerjee, Ayan
Sent: Tuesday, July 08, 2008 3:57 PM
To: sv-bc@server.eda-stds.org
Subject: [sv-bc] Query about '1



Hi,



I have 3 queries about what should be the correct behavior for the following
3 cases.



1)

What should be behavior if '1 is passed to a port as is done in the
following testcase?



module top;

bottom inst('1);

endmodule



module bottom(a);

input [63:0] a;



initial

    $display("%b", a);

endmodule



 Should it be a)
1111111111111111111111111111111111111111111111111111111111111111 or

                    b)
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz1 or

                    c)
0000000000000000000000000000000000000000000000000000000000000001



[SB] a. This should be treated as the continuous assignment "bottom.a = '1"
. 





2) What should be the behavior if '1 is used as parameter value

module top;

parameter [63:0] p1 = '1;

initial

    $display("%b",p1);

endmodule



Should it be a)
1111111111111111111111111111111111111111111111111111111111111111 or

                  b)
0000000000000000000000000000000000000000000000000000000000000001



[SB] a. Treated as assignment "p1[63:0] = '1". 



3) Similar to 2 but in a more general case what should be the value of
parameter if range is specified which is more than 32 but the expression
assigned is of 32 bit. Should the expression be evaluated in 32 bit or with
the size of parameter?



module top;

parameter [63:0] p1 = 1'b1 << 63;

initial

    $display("%b",p1);

endmodule



Should it be a)
0000000000000000000000000000000000000000000000000000000000000000  or

                  b)
1000000000000000000000000000000000000000000000000000000000000000



The behavior of simulators are different in the above cases. Thanks in
advance for your help.

 [SB] With the size of the parameter. The answer should be b. We discussed
this in the past.



Shalom









-Regards,

Ayan

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