[sv-bc] Modport expression examples

In Draft 7a, 25.5.4 has the following examples of modport expressions:

interface I;
logic [7:0] r;
const int x=1;
bit R;
modport A (output .P(r[3:0]), input .Q(x), R);
modport B (output .P(r[7:4]), input .Q(2), R);
endinterface

I'm in doubt about the Q ports.

The first example is

const int x=1;
modport A (output .P(r[3:0]), input .Q(x), R);

I question this for two reasons. First, x is of type int, which is a 2-state type.
The rules state that "input int x" should not be legal because it defaults to a net type and 2-state types are not allowed to be nets, so the keyword "var" should need to be added.

Second, because x is declared as const. How can a module input be const?
x is the internal name of the port, whereas Q is the external name.

Similarly,
modport B (output .P(r[7:4]), input .Q(2), R);

This looks wrong also. The input port Q is an alias for "2", which does not make sense either.

In fact, none of the tools I checked allowed this syntax:
module m(.Q(2));

It looks to me as though the author of the example got confused about the explicit port declaration syntax, as often happens, and related to it like a port connection, not like a port declaration.

For input port connections, you could say that x or 2 drive Q, but as input port declarations, it is reversed.

Comments?

Thanks,
Shalom

Shalom Bresticker
Intel Jerusalem LAD DA
+972 2 589-6582
+972 54 721-1033


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