Difference between revisions of "Verilog Port Expressions"
From Verific Design Automation FAQ
| Line 1: | Line 1: | ||
| − | '''Q: Why are the ports in original Verilog file renamed to | + | '''Q: Why are the ports in original Verilog file renamed to p1, p2, ....?''' |
Input file: | Input file: | ||
| Line 12: | Line 12: | ||
Output netlist: | Output netlist: | ||
| − | module foo ( | + | module foo (p1, p2, p3, , p7); // test.v(1[8:11]) |
| − | input | + | input p1; // test.v(6[17:23]) |
| − | input | + | input p2; // test.v(6[17:23]) |
| − | input [1:0] | + | input [1:0]p3; |
| − | input [2:0] | + | input [2:0]p7; |
... | ... | ||
endmodule | endmodule | ||
Revision as of 13:34, 23 December 2020
Q: Why are the ports in original Verilog file renamed to p1, p2, ....?
Input file:
module foo ( datain[0], datain[0] /* same net into multiple port expression */,
datain[2:1] /* part-select port expression */,
/* empty port expression */,
{datain[2],datain[1], datain[1]} /* concatenation in port expression */
) ;
input [2:0] datain ;
...
endmodule
Output netlist:
module foo (p1, p2, p3, , p7); // test.v(1[8:11])
input p1; // test.v(6[17:23])
input p2; // test.v(6[17:23])
input [1:0]p3;
input [2:0]p7;
...
endmodule
The items in the () after the module name are not "port names," rather, they are "port expressions." Verilog defines that the port expressions on this module CANNOT be accessed by name (only by order). This means you cannot rely on the port names to be one thing or another.
Verific chose to not adjust to any particular naming scheme for complex port expressions, which also allows us to error out if named port instantiation occurs where the language disallows it.
The original port expression of the renamed port is saved as attributes " orig_port_name" attached to the port.
key: " orig_port_name", value: port expression
For the testcase above:
input p1 /* verific orig_port_name=datain[0] */ ; input p2 /* verific orig_port_name=datain[0] */ ; input [1:0]p3 /* verific orig_port_name=datain[2] datain[1] */ ; input [2:0]p7 /* verific orig_port_name=datain[2] datain[1] datain[1] */ ;
