Subject: RE: Handling of "implicit" declarations
From: David Smith (david_smith@avanticorp.com)
Date: Mon Sep 24 2001 - 11:24:51 PDT
Also, how do you do partial change of an interface? I have one branch I want to modify to be implemented at the cell level and the rest at the system level. I have to change the definition of just those interfaces do I not? Is this not similar to having to change declarations? Help me understand since it is not clear.
David
-----Original Message-----
From: Stefen Boyd [mailto:stefen@boyd.com]
Sent: Monday, September 24, 2001 11:16 AM
To: David Smith
Cc: 'vlog-pp@eda.org'
Subject: Re: Handling of "implicit" declarations
At 11:33 AM 9/20/2001 -0700, David Smith wrote:
>of modules A2, B2, C2, and C3 to be an RTL implementation. These have net/reg ports. Now all instance of all parents must be changed from interfaces to net/reg ports etc...
David,
This is not true... You don't have to change any parent
definitions:
1) Just because you change the implementation to
rtl doesn't mean you have to throw away
the interface... the interface just has to
contain nets/regs instead of abstract stuff.
2) Even if the rtl implementation of the lower level
modules don't use the interface as a whole,
the interface can be used to connect to a
Verilog 2001 module. A simple example was
provided in the ESS 3 doc on page 59. Note
that modules lightWires and switchWires are
an example of this. If you want to limit what
gets used, then define a modport and use
interface.modport to specify the connectivity.
So you might change the interface definition from
an abstract model of the communication to a bundle
of wires, etc. but you don't have to stop using
interfaces just because you changed an implemented
module... That's the whole reason for using interfaces!
You get the best of both worlds: you get explicit and
concise declarations AND you can change the implementation
from abstract to implementation without modification
to the entire hierarchy.
Regards,
Stefen
--------------------
Stefen Boyd Boyd Technology, Inc.
stefen@BoydTechInc.com (408)739-BOYD
www.BoydTechInc.com (408)739-1402 (fax)
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