[sv-ec] RE: Query on bin value with x or z bits

Friendly reminder !!

Please let us know your comments on this.

Thanks,
Devraj

From: Devraj Goyal
Sent: Tuesday, July 27, 2010 5:33 PM
To: sv-ec@eda.org
Subject: Query on bin value with x or z bits

I have a query regarding value of coverbin when open_range_list yields a value with x or z bits.

Example:
logic [3:0] cp_var;
covergroup cg;
            CP: coverpoint cp_var{
                        bins b1 = {4'b1zx0, 4'b01xz};
                        bins b2 = {[4'b1zx0:4'b01xz]};
                        bins b3[] = {[4'b1zx0:4'b01xz]};
            };
endgroup

P1800-2009 LRM says (sec 19.5.3)
"When a bin definition includes an X or Z,
it indicates that the bin count should only be incremented when the sampled value has an X or Z in
the same bit positions, i.e., the comparison is done using ===."

Sec (19.5.6) says a warning needs to be given if open_range yields a value with any x or z bits for non wildcard bins,
and the following rules will be applied:

1) If an element of a bins open_range_list is a singleton value b, the element shall not participate in
the bins values.
2) If an element of a bins open_range_list is a range [b1 : b2] and either b1 or b2 contains any x or
z bits or every value in the range would generate a warning, then the element shall not participate in
the bins values.

Both these comments seem to be contradicting.
Should we always ignore X/Z values for non wildcard bins?

Please let us know what should be the correct behavior.

Also, is it valid to specify open_range_list as defined in bins b2 and b3.

Thanks,
Devraj

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