port_discipline

All,

In the LRM 2.2 Annex E.3.3.1 the discipline of analog primitives can be
resolved by means of the port_discipline arttibute. An example of this port
discipline attribute is given. It is:

resistor #(.r(1k)) (* integer port_discipline="electrical" ; *) r1
(node1, node2); // not needed as default
resistor #(.r(1k)) (* integer port_discipline="rotational" ; *) r2
(node1, node2);

The integer type in these attribute instances is wrong anyway, so this has
to be changed.

Additionally, according to the syntax in Annex A of IEEE 1364-2005 as well
as the syntax proposal for LRM 2.3, this is not the correct place for an
attribute instance. Instead, the attribute instance should be in front of
each of the port connections. This would change the example to:

resistor #(.r(1k)) r1
((* port_discipline="electrical" ; *) node1, (*
port_discipline="electrical" ; *) node2); // not needed as default
resistor #(.r(1k)) r2
((* port_discipline="rotational" ; *) node1, (*
port_discipline="rotational" ; *) node2);

This makes sense as the port_discipline should be related to the port, not
to the module instance. This allows also for multi discipline ports. As an
example, the self-heating version of the Mextram BJT model has 4 electrical
ports and one thermal port. With the LRM 2.2 it would not be possible to
correctly set the port disciplines for this built-in model, while the
1364-2005 compliant syntax would allow this.

Should we update the syntax to allow attribute instances in the location
suggested by LRM 2.2, or should we change the example in E.3.3.1 to reflect
the syntax of 1364-2005? I'm in favor of the latter, but I don't know if
there are backwards compatibility issues by explicitly making the example
E.3.3.1 erroneous.

Cheers,
Marq
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