RE: [sv-ac] SV-AC new errata - 1547

Hi Ed,

 

I think I responded to part of this earlier but am responding to the
other part now.  I'd still like to hear from others what they think
about allowing assertion directives in clocking blocks.   It just seems
like an arbitrary rule that impacts a user's methodology.   

 

Lisa

 

________________________________

From: Eduard Cerny [mailto:Eduard.Cerny@synopsys.com] 
Sent: Thursday, July 20, 2006 2:06 PM
To: Lisa Piper; sv-ac@eda-stds.org
Subject: RE: [sv-ac] SV-AC new errata - 1547

 

Lisa, 

 

would you allow references to properties declared outside the clocking
block in concurrent_assertion_item which is placed in a clocking block?

[Lisa Piper >>>] I guess you could.  I would not recommend that
methodology personally, but if you want to assert properties that are
defined in a package then this might be one way to do it.

 

Also, the clocking block cannot exist on its own, i.e., it mus be placed
in a module, interface or program. Therefore, if the assertion is
outside the enclosure containing the clocking block, it will also have
to have an XMR. If it is inside, the XMR is local and I do not see how
it would affect portability.

[Lisa Piper >>>]  I think it is pretty clear that I did not understand
this point.  I agree that portability is not an issue.

 

So... I am not that sure about necessity for the enhancement. Can you
give an example where the current situation is a hindrance?

[Lisa Piper >>>] I still think it is good methodology to keep the
property definition and assertion of the property local.  It just seems
like an unnecessary rule that the user will run into when they compile. 

 

Best regards,

ed

 

	 

	
________________________________


	From: owner-sv-ac@eda-stds.org [mailto:owner-sv-ac@eda-stds.org]
On Behalf Of Lisa Piper
	Sent: Thursday, July 20, 2006 1:58 PM
	To: sv-ac@verilog.org
	Subject: [sv-ac] SV-AC new errata - 1547

	I have just opened a new Mantis entry - #1547.  I had asked for
some feedback earlier and did not get much response (one was for and one
against).  Anyway, I think this is important from a methodology
perspective so would like to get more feedback. For convenience the
proposal is repeated below.

	 

	Lisa

	 

	=======================

	 

	Overview:

	 

	The way the standard is currently written, you cannot associate
a verification directive with properties that are defined inside of a
clocking block.  The only way to assert the property is to use a
hierarchical reference to the name of the property.  This is undesirable
for three reasons:

	1)      relying on hierarchical references affects code
portability

	2)      many methodologies recommend keeping the property
definition and its associated verification directive local for ease of
debug

	3)      the ability to instantiate properties from packages in a
clocking block

	 

	This proposes changes to allow for specifying verification
directives inside clocking blocks.

	 

	=======

	 

	 

	DETAILS:

	 

	Replace A.6.11 (and associated text in 15.2) 

	 

	clocking_declaration ::=

	[ default ] clocking [ clocking_identifier ] clocking_event ;

	{ clocking_item }

	endclocking [ : clocking_identifier ]

	 

	clocking_event ::=

	@ identifier

	| @ ( event_expression )

	 

	clocking_item ::=

	default default_skew ;

	| clocking_direction list_of_clocking_decl_assign ;

	| { attribute_instance } concurrent_assertion_item_declaration

	 

	 

	 

	WITH

	 

	 

	clocking_declaration ::=

	[ default ] clocking [ clocking_identifier ] clocking_event ;

	{ clocking_item }

	endclocking [ : clocking_identifier ]

	 

	clocking_event ::=

	@ identifier

	| @ ( event_expression )

	 

	clocking_item ::=

	default default_skew ;

	| clocking_direction list_of_clocking_decl_assign ;

	| { attribute_instance } concurrent_assertion_item_declaration

	| concurrent_assertion_item

	 

	 

	 

	 

	REPLACE (in 17.13)

	 

	A concurrent assertion statement can be specified in any of the
following:

	- An always block or initial block as a statement, wherever
these blocks can appear

	- A module

	- An interface

	- A program

	 

	WITH

	 

	A concurrent assertion statement can be specified in any of the
following:

	- An always block or initial block as a statement, wherever
these blocks can appear

	- A module

	- An interface

	- A program

	- A clocking block