Regards,
-Anand
From: Greg
Jaxon [mailto:Greg.Jaxon@synopsys.com]
Sent: Tuesday, May 26,
2009 11:17
PM
To: Bresticker, Shalom
Cc: Anand Gurusamy;
sv-bc@server.eda.org; Arun Maity;
Girish Ravunnikutty; Kapil Kaushik
Subject: Re: [sv-bc]
9058:
Specifying modport on array of interfaces; a Proposal
Yes, I believe this is the same issue.
Both of Anand's example cases conform to BNFs that already exist in
Annes A and
elsewhere.
Either will work. Furthermore, per section 25.5,
If a port connection specifies a modport list
name in both the
module instance and module header
declara-
tion, then the two modport list names shall be identical. [emphasis
added]
... so the two can be combined. [One
defect I notice in this section's prose is the unwarranted bias that
the "down design" to which the interface's modport connects is a
"module", when it might also be another
interface.]
In 9058 and in the present case, some doubt exists because the prose
never
refers to the unpacked
dimension syntax; nor does it explain how the dimensions of an
interface instance
interact with
the modport access restrictions. We've never formally introduced the
concept of an "array of interface
modports", though the BNF suggests these exist.
The existing prose in section 25.5 was written in the spirit of
examples being
more definitive than the text,
but for the text to be entirely accurate in everything, it would become
even
more unreadable than it is already.
I'd recommend leaving it in its current "gentle tutorial" form and
adding the array of modport concept in a
new subsection devoted to resolving the question that wasn't asked in
either
9058 or this thread.
Add:
25.5.n Modport and
interface array expressions for use in port connections
The ports in a list_of_interface_identifiers
have
(possibly empty) sets of unpacked_dimensions; the corresponding actual
port expressions must have a matching set of unpacked_dimensions (or a
matching
lack thereof). Both the modport specification and the unpacked
dimensions
are additional matching criteria to the interface named type used on
this port
connection. The three properties (named type, modport, and dimensions)
are completely orthogonal. In an interface port actual expression, the
optional .modport_identifier
clause may
appear as a subfield selection anywhere in the static prefix of the
actual
interface (see section 11.5.3). It is an error for a modport selection
to
be applied to an interface type which does not declare that modport
identifier,
or to an interface type which already has a different
modport identifier specified; redundantly specifying the same modport
is not
prohibited.
Also add to Section 23.3.3.4
the
following paragraphs:
If a port declaration with either a generic
or a named
interface type has a modport specification, it serves to either select
or
confirm the modports being connected. If the actual port expression
delivers an interface type without a particular modport specification,
the
formal modport identifier must exist within the actual interface type
being
connected, and only the connections it specifies shall be made between
corresponding elements of the actual and formal ports. If the actual
port expression adds a modport specification, or refers to an interface
type
for which a modport has already been specified, it must match the
declaration's
modport, and again only the modport connections are made.
A modport specification may be given as a subfield selection anywhere
within
the static prefix of an interface port expression.
Greg Jaxon
Bresticker, Shalom wrote:
From:
owner-sv-bc@server.eda.org
[mailto:owner-sv-bc@server.eda.org]
On Behalf Of Anand
Gurusamy
Sent: Monday, May
25, 2009 3:04 PM
To: sv-bc@server.eda.org
Cc: Arun Maity; Girish Ravunnikutty; Kapil
Kaushik
Subject: [sv-bc]
Specifying
modport on array of interfaces..
Hi there,
Here we are trying to use
array of interfaces and
specify modport.
In case-1, we instantiate
array of interfaces in the
submodule and specify the modport list name in the top level module
And in case-2, we
instantiate the array of interface
along with modport specified.
So, could you please
clarify which one would be the
correct way?
Thanks and Regards,
-Anand
***********************************************
* CASE 1:
***********************************************
interface inf ();
logic din;
logic dout;
modport
x(output dout, input
din);
modport y(inout
dout, inout
din);
endinterface: inf
module sub(in, U1, out);
input [1:0] in;
output [1:0] out;
inf U1 [2];
endmodule
module top(in, out);
input [1:0] in;
output [1:0] out;
inf U1 [2] ();
sub inst_sub
(.U1(U1.x),.in(in),
out(out));
endmodule
***********************************************
* CASE 2:
***********************************************
interface inf ();
logic din;
logic dout;
modport
x(output dout, input
din);
modport y(inout
dout, inout
din);
endinterface: inf
module sub(in, U1, out);
input [1:0] in;
output [1:0] out;
inf.x U1[2];
endmodule
module top(in, out);
input [1:0] in;
output [1:0] out;
inf U1 [2] ();
sub inst_sub (.U1(U1),
.in(in),
out(out));
endmodule
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