RE: [sv-bc] RE: [sv-ec] Inconsistencies in virtual interfaces and modports

>I tried to use an interface *without* modports in synthesis - but I am
sure that
>at some time in the past I did so [...] and got away with it.

In synthesis, if an interface has no variables, but only nets with their
default 'inout' direction, then modports are not required, although they
are still recommended.

-- Brad 

-----Original Message-----
From: Jonathan Bromley [mailto:jonathan.bromley@doulos.com] 
Sent: Monday, July 23, 2007 6:28 PM
To: Brad Pierce; sv-ec@eda-stds.org; sv-bc@eda-stds.org
Subject: RE: [sv-bc] RE: [sv-ec] Inconsistencies in virtual interfaces
and modports

Brad,

Many thanks for your helpful response.

> In synthesis, access to an interface variable via an interface-type 
> module port requires that a modport be used and that the modport 
> impose an 'input' or 'output' direction on the interface variable to 
> override the default 'ref' semantics.

Indeed it does, in 2 of the 3 synthesis tools I can try that understand
interfaces.  It has been a long time since I tried to use an interface
*without* modports in synthesis - but I am sure that at some time in the
past I did so, in Synopsys tools, and got away with it.  Has this
restriction been imposed recently, or is it simply that my memory is
deceiving me?

Anyway, given all the clarifications from you and others, it's obvious
to me that your model of modport inputs and outputs creating continuous
assignments is the right one.  From the point of view of exposition in
the LRM, that also implies that the modport appearing in a module's port
list must create a group of variables, one for each input and output
member, in the module itself.

I'm sorry it has taken so long for the penny to drop with me.
However, I humbly suggest that there is some evidence that the LRM needs
some clearing-up!  And there remains the virtual interfaces
problem......

Thanks again to all
--
Jonathan Bromley, Consultant

DOULOS - Developing Design Know-how
VHDL * Verilog * SystemC * e * Perl * Tcl/Tk * Project Services

Doulos Ltd. Church Hatch, 22 Market Place, Ringwood, Hampshire, BH24
1AW, UK
Tel: +44 (0)1425 471223                   Email:
jonathan.bromley@doulos.com
Fax: +44 (0)1425 471573                           Web:
http://www.doulos.com

The contents of this message may contain personal views which are not
the views of Doulos Ltd., unless specifically stated.

-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.