RE: [sv-bc] MERGE REVIEW draft 2: Chapter 6

Thanks.

There is no reason why a UDP output could not be of type 'logic'.

What about the 2-state type 'bit'?

What are arguments for and against?

Thanks,
Shalom

> -----Original Message-----
> From: owner-sv-bc@server.eda.org [mailto:owner-sv-bc@server.eda.org]
> On Behalf Of Brad Pierce
> Sent: Wednesday, April 18, 2007 12:57 AM
> To: sv-bc@server.eda-stds.org
> Subject: Re: [sv-bc] MERGE REVIEW draft 2: Chapter 6
> 
> Shalom writes --
> 
> >Finally, I saw one place in the BNF where 'reg' is required twice
> >instead of logic, in A.5.2:
> 
> This is the topic of
> 
>    http://www.eda-stds.org/svdb/bug_view_page.php?bug_id=0001368
> 
> -- Brad
> 
> [ In reply to http://www.eda-stds.org/sv-bc/hm/5824.html . ]
> 
> -----Original Message-----
> From: Bresticker, Shalom [mailto:shalom.bresticker@intel.com]
> Sent: Monday, April 16, 2007 1:30 AM
> To: Brad Pierce; sv-bc@eda-stds.org
> Subject: RE: [sv-bc] MERGE REVIEW draft 2: Chapter 6
> 
> Brad,
> 
> > 6.3 -- "Nets cannot be written by procedural statements. ...  A net
> > cannot be procedurally assigned."  Is there a difference between
> these
> 
> > two?
> 
> [SB] Probably not.
> 
> 
> > 6.3 -- "Variables can be written by one continuous assignment or one
> > port."  I guess this means by an output port, but isn't that
> > necessarily a continuous assignment?  What's the need for adding "or
> > one port"?
> 
> [SB] I also see no need.
> 
> 
> > 6.5 -- "The keywords logic and reg are equivalent types (see 6.20.2
> > for details on type equivalence)."  A keyword is not a type.  I
> think
> > that the 'logic' and 'reg' data types are at least matching, not
> > merely equivalent, and are perhaps even identical types.  I see no
> > details about this issue in the cross-referenced 6.20.2.
> 
> [SB] I agree (except for the few lexical restrictions on reg), but
> this
> goes back to 1800-2005. Twice it says there that they are equivalent
> and
> references the equivalence rules, in 4.3.2 and in 6.1. 27.14 Detail
> (s)
> says, "SystemVerilog treats reg and logic variables as equivalent in
> all
> respects."
> 
> Also, in 15.14.2, there is an example with the following sentence that
> probably should be reworded:
> "The driven value of nibble is 4'b0xx1, regardless of whether nibble
> is
> a reg or a wire."
> 
> Finally, I saw one place in the BNF where 'reg' is required twice
> instead of logic, in A.5.2:
> 
> udp_output_declaration ::=
>   { attribute_instance } output port_identifier
> | { attribute_instance } output reg port_identifier
>                                              [ = constant_expression ]
> 
> udp_reg_declaration ::= { attribute_instance } reg variable_identifier
> 
> 
> > 6.6.1 -- "specified by the lsb" Unnecessary italics.
> 
> [SB] Also, "the msb" in the previous line, "the" should not be in
> italics.
> 
> 
> > 6.6.1 -- "Vector nets and vectors of reg, logic and bit types shall
> be
> > treated as
> > unsigned quantities, unless declared to be signed or is connected to
> a
> > port that is declared to be signed (see 22.8.3)."  Again there's a
> > mixing of kind and type.  The type of a net could be logic vector.
> > Also, how does connecting a vector to a signed port cause it to be
> > treated as a signed quantity?  There's no example using a port
> > connection in the examples that immediately follow.  And there's
> > nothing
> > about this in the cross-referenced section, which regards parameter
> > value assignments.
> 
> [SB] This comes from 1364-2005, section 4.3.1, where the original text
> is, "Vector nets and regs shall be treated as unsigned quantities,
> unless the net or reg is declared to be signed or is connected to a
> port
> that is declared to be signed (see 12.2.3)."
> 
> The cross-reference there is incorrect also. The correct reference in
> 1364 is 12.3.3, where it says,
> 
> "The signed attribute can be attached either to a port declaration or
> the corresponding net or reg declaration or to both. If either the
> port
> or the net/reg is declared as signed, then the other shall also be
> considered signed.
> 
> Implicit nets shall be considered unsigned. Nets connected to ports
> without an explicit net declaration shall be considered unsigned,
> unless
> the port is declared as signed."
> 
> 
> > 6.18 and 6.18.5, "local constant"?   Maybe it's OK, but worth having
> a
> > discussion about this newly added terminology, that is used only
> twice
> > in the draft LRM.
> 
> [SB] This term is used in 1800-2005 only once, in the section
> corresponding to 6.18.5 here. I don't like it, although 1364 is
> responsible for the term 'local parameter'.
> 
> Thanks,
> Shalom
> 
> --
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