-----Original Message----- From: Francoise Martinolle Sent: Thursday, March 01, 2007 12:33 PM To: 'Jonathan Bromley'; sv-bc@eda-stds.org Subject: RE: [sv-bc] Are modport port directions enforced? I think that there are differences, subtle but visible. When you write to an output the write has to propagate up to the object connected in the parent module instance. when you write to a ref port, you are writing to the original object and that write is immediately visible. Because there is a continuous assignment from the output port to the connected object, there may or may not be an extra cycle (depending if the continuous assignment for propagation is inlined with the write operation or not). If you write the output with a force statement, I think that only that output is forced but not the object connected to it. That is not the case for the ref port, the original object would be forced. Francoise ' -----Original Message----- From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of Jonathan Bromley Sent: Thursday, March 01, 2007 8:54 AM To: sv-bc@eda-stds.org Subject: RE: [sv-bc] Are modport port directions enforced? [Shalom] > According to this interpretation, variables are passed as ref ports, > which really do reference the original, and one could look at nets as > using port collapsing. Does that make sense? Not to me. If it is that way, what is the difference between "ref" and "output" in a modport, given that port mode "output" has never stopped us reading things? -- 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. -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.Received on Thu Mar 1 12:54:06 2007
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