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

 

 

________________________________

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 think it would be allowed, though it is not something
that I would particularly recommend.  

 

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 of the clocking block as another scope, the
only difference being that it cannot be standalone.  I did not know
there was a concept of a "local XMR".  I thought it would always be full
path.  Is the "local XMR" described in the standard?

 

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 >>>] as a user, it seems like an unnecessary rule that I
will learn after I make the mistake and have the compiler tell me
several times. If I can put a property or sequence there, then I don't
see why I should not be able to put an assertion there.  And again, I
like to see them together for the purpose of debug.  

 

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