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<a href="#" onmousedown="showPopup(this, 'popup00404');"><img src="seealsolink.png" border="0" alt="" title=""></a> SystemVerilog 3.1a语言参考手册</div>
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19.4 modport</div>
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To restrict interface access within a module, there are modport lists with directions declared within the interface. The keyword modport indicates that the directions are declared as if inside the module. </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00835"><pre class="Element12">interface i2;
wire a, b, c, d;
modport master (input a, b, output c, d);
modport slave (output a, b, input c, d);
endinterface</pre></div></div>
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In this example, the modport list name (master or slave) can be specified in the module header, where the interface name selects an interface and the modport name selects the appropriate directional information for the interface signals accessed in the module header. </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00836"><pre class="Element12">module m (i2.master i);
...
endmodule
module s (i2.slave i);
...
endmodule
module top;
i2 i();
m u1(.i(i));
s u2(.i(i));
endmodule</pre></div></div>
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The syntax of interface_name.modport_name reference_name gives a local name for a hierarchical reference. Note that this can be generalized to any interface with a given modport name by writing interface.modport_name reference_name. The modport list name (master or slave) can also be specified in the port connection with the module instance, where the modport name is hierarchical from the interface instance. </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00837"><pre class="Element12">module m (i2 i);
...
endmodule
module s (i2 i);
...
endmodule
module top;
i2 i();
m u1(.i(i.master));
s u2(.i(i.slave));
endmodule</pre></div></div>
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If a port connection specifies a modport list name in both the module instance and module header declaration, then the two modport list names shall be identical. </p>
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In a hierarchically nested interface, the directions in a modport declaration can themselves be modport plus name. </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00838"><pre class="Element12">interface i1;
interface i3;
wire a, b, c, d;
modport master (input a, b, output c, d);
modport slave (output a, b, input c, d);
endinterface
i3 ch1(), ch2();
modport master2 (ch1.master, ch2.master);
endinterface</pre></div></div>
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All of the names used in a modport declaration shall be declared by the same interface as is the modport itself. In particular, the names used shall not be those declared by another enclosing interface, and a modport declaration shall not implicitly declare new ports. No hierarchical references shall be permitted within a modport. </p>
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The following interface declarations would be illegal: </p><div class="Element170">
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<div class="Element13"><div class="Element12" id="code00839"><pre class="Element12">interface i;
wire x, y;
interface illegal_i;
wire a, b, c, d;
// x, y not declared by this interface
modport master(input a, b, x, output c, d, y);
modport slave(input a, b, x, output c, d, y);
endinterface : illegal_i
illegal_i ch1(), ch2();
modport master2 (ch1.master, ch2.master);
endinterface : i
interface illegal_i;
// a, b, c, d not declared by this interface
modport master(input a, b, output c, d);
modport slave(output a, b, output c, d);
endinterface : illegal_i</pre></div></div>
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Note that if no modport is specified in the module header or in the port connection, then all the nets and variables in the interface are accessible with direction inout or ref, as in the examples above.</p></div>
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描述 </div></td></tr><tr>
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<a href="00220.html" target="topic">19.4.1 An example of a named port bundle</a> </div></td><td class="Element206" valign="top" width="50%">
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This interface example shows how to use modports to control signal directions as in port declarations. It uses the modport name in the module definition. </div></td></tr><tr>
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<a href="00221.html" target="topic">19.4.2 An example of connecting a port bundle</a> </div></td><td class="Element206" valign="top" width="50%">
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This interface example shows how to use modports to restrict interface signal access and control their direction. It uses the modport name in the module instantiation. </div></td></tr><tr>
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<a href="00222.html" target="topic">19.4.3 An example of connecting a port bundle to a generic interface</a> </div></td><td class="Element206" valign="top" width="50%">
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This interface example shows how to use modports to control signal directions. It shows the use of the interface keyword in the module definition. The actual interface and modport are specified in the module instantiation. </div></td></tr><tr>
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<a href="00223.html" target="topic">19.4.4 Modport expressions</a> </div></td><td class="Element206" valign="top" width="50%">
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A modport expression allows elements of arrays and structures, concatenations of elements, aggregate expressions of elements declared in an interface to be included in a modport list. This modport expression is explicitly named with a port identifier, visible only through the modport connection.<br><br>Like explicitly named ports in a module port declaration, port identifiers exist in their own namespace for each modport list. When modport item is just a simple port identifier, that identifier is used as both a reference to an interface item and a port identifier. Once a port identifier has been defined, there shall not be another... <a href="00223.html" target="topic">more</a> </div></td></tr><tr>
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<a href="00224.html" target="topic">19.4.5 Clocking blocks and modports</a> </div></td><td class="Element206" valign="top" width="50%">
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The modport construct can also be used to specify the direction of clocking blocks declared within an interface. As with other modport declarations, the directions of the clocking block are those seen from the module in which the interface becomes a port. The syntax for this is shown below. </div></td></tr></table></div></div>
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