Checkers - SVA: The Power of Assertions in SystemVerilog - page 197

9.3.1.1 Positional Association

In module m1 below, the actual arguments of the checker are passed according to
the order of the corresponding formal arguments. The default values passed to n and
clk are identified by commas, one comma for each unspecified actual argument.
Were these default arguments the last arguments in the list, there would be no need
for these commas. Positional argument association is really convenient only when
the number of checker arguments is small.

module m1( input logic clk, rst, send, ack, ...);
default clocking @( posedge clk); endclocking
...
request_granted check(send, ack,,, rst);
endmodule :m1

9.3.1.2 Explicit Named Association

In module m2 below, the actual arguments of the checker are passed by an explicit
indication of the formal argument names. In the case of the named association, the
order of the actual arguments is not important. Omitting default values does not
require any additional notation. A named association is convenient when the number
of checker arguments is large, or when the default values are passed to the arguments
in the middle of the argument list.

module m2( input logic clk, rst, send, ack, ...);
default clocking @( posedge clk); endclocking
...
request_granted check(.rst(rst), .req(send), .gnt(ack));
endmodule :m2

9.3.1.3 Implicit Named Association

When the names of actual and formal arguments coincide, there is no need to repeat
the argument names. In module m3 , argument rst is passed by implicit named
association.

module m3( input logic clk, rst, send, ack, ...);
default clocking @( posedge clk); endclocking
...
request_granted check(.rst, .req(send), .gnt(ack));
endmodule :m3