Re: BE55

From: Shalom Bresticker (r50386@email.sps.mot.com)
Date: Thu Oct 21 1999 - 05:20:56 PDT

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Anders Nordstrom wrote:
<BLOCKQUOTE TYPE=CITE>
<UL>
<LI>
BE55 - This one doesn't seem to be implemented at all....</LI>

Replace the first paragraph in section 3.5 on page
21 with:

The syntax shown in Section 3.2 shall be used to declare nets and
registers explicitly. In the absence of an explicit declaration,
 an implicit net of default net type shall be assumed in the following
circumstances:</UL>
</BLOCKQUOTE>

The concept of "default net type" has not yet been defined at this
point.
 I suggest to delete "of default net type" here. The net
type is defined below.
 
<BLOCKQUOTE TYPE=CITE>
<UL>- If an identifier is used in a port expression declaration, then
an implicit net of type wire shall be assumed, with the vector width of
 the port expression declaration. See Section 12.3.2 for a discussion
of port expression declarations.</UL>
</BLOCKQUOTE>

Question: implicit net of type wire or of default net type
?
 The wording of 12.3.2, below, says that default net type is used.
 I suggest to delete "of type wire" here. The net type is
defined below.
 
<BLOCKQUOTE TYPE=CITE>
<UL>- If an identifier is used in the terminal list of a primitive instance
or a module instance, and that identifier has not been
 explicitly declared previously in one of the declaration statements
of the instantiating module, then an implicit scalar net of
 default net type shall be assumed.</UL>
</BLOCKQUOTE>

Similarly, delete "of default net type" here. The net
type is defined immediately below.
 Also need to add case of LHS of continuous assignment.

The second paragraph of 3.5 is confusing. It says:

"These implicitly declared nets shall be treated as scalar nets of type
wire. See Section 19 for a discussion of control of the type for implicitly
declared nets with the `default_nettype compiler directive."

These two sentences seems to contradict each other. Better is
as written below:

The implicit net data type shall be wire, unless another default
type has been directed.
 See Section 19.2 for a discussion of control of the type for implicitly
 declared nets using the `default_nettype compiler directive.

Note that in contrast to what is currently written in 3.5, implicit
nets are not necessarily scalars.
 That is, in the case of port expressions, they take the width of the
port expression.
 
<BLOCKQUOTE TYPE=CITE>
<UL>In section 12.3.2 on page 174. Chage the sentence "A port can be declared
in both a port declaration and a net or register declaration.
 If a port is declared as a vector, the range specification
between the two declarations of a port shall be identical. " to:

A port_expression which is an identifier can be declared in both
a port declaration and a net or register declaration. A net or register
 declaration establishes the data type of the
 internal net or register connected to the port. If no net or register
declaration is made for the port_expression identifier,
 then a default data type is assumed.

An explicit net or register declaration for an identifier which is
also used in a port_expression declares the specific data type
 and vector size of the port_expression. If the vector
 range of a data type declaration differs from the vector range of
a port_expression declaration for the same identifier,
 the declaration of the net or register shall be used.

If there is no explicit net or register declaration for an identifier
used in a port_expression declaration, then an implicit net shall be assumed,
 with the vector width of the port_expression declaration. The implicit
net data type shall be wire, unless another default type has been directed.
 See Section 19.2 for a discussion of control of the type for implicitly
 declared nets using the `default_nettype compiler directive. This
implicit net type shall be used for the internal net type when the rules
 for connecting dissimilar ports are applied.
 These rules are discussed in Section 12.3.6 and Section 12.3.8.</UL>
</BLOCKQUOTE>
This can be shortened as follows, I think:

A port_expression which is an identifier can be declared in both
a port declaration and a net or register declaration.

A net or register declaration establishes the data type and vector
range of the port_expression.
 If the vector range of a data type declaration differs from the
vector range of a port_expression declaration for the same identifier,
 the declaration of the net or register shall be used.

If no net or register declaration is made for the port_expression
identifier, then a default data type is assumed, as described in Section
3.5.
 This implicit net type shall be used for the internal net type when
the rules for connecting dissimilar ports are applied.
 These rules are discussed in Section 12.3.6 and Section 12.3.8.
<PRE>--

************************************************************************
Shalom Bresticker email: shalom@msil.sps.mot.com
Motorola Semiconductor Israel, Ltd. Tel #: +972 9 9522268
P.O.B. 2208, Herzlia 46120, ISRAEL Fax #: +972 9 9522444
<A HREF="http://www.motorola-semi.co.il/"><a href="http://www.motorola-semi.co.il/">http://www.motorola-semi.co.il/>>
************************************************************************</PRE>

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