Section A.2.4, Syntax 6-5, 6.20.1
Mantis 907: Default parameter assignments should be optional

In A.2.4 and Syntax 6-5, REPLACE

param_assignment ::=

parameter_identifier { unpacked_dimension } = constant_param_expression

specparam_assignment ::=

specparam_identifier = constant_mintypmax_expression

| pulse_control_specparam

type_assignment ::=

type_identifier = data_type

WITH

param_assignment ::=

parameter_identifier { unpacked_dimension } [ = constant_param_expression ]⁹⁹

specparam_assignment ::=

specparam_identifier = constant_mintypmax_expression

| pulse_control_specparam

type_assignment ::=

type_identifier [ = data_type ] ⁹⁹

⁹⁹In a param_assignment it shall be illegal to omit the constant_param_expression except within a parameter_declaration in a parameter_port_list. In a type_assignment it shall be illegal to omit the data_type except within a parameter_declaration in a parameter_port_list.

In 6.20.1, REPLACE

The parameter keyword can be omitted in a parameter port list. For example:

class vector #(size = 1); // size is a parameter in a parameter port list

logic [size-1:0] v;

endclass

interface simple_bus #(AWIDTH = 64, type T = word) // parameter port list

(input bit clk) ; // port list

...

endinterface

In a list of parameter constants, a parameter can depend on earlier parameters. In the following declaration, the default value of the second parameter depends on the value of the first parameter. The third parameter is a type, and the fourth parameter is a value of that type.

module mc #(int N = 5, M = N*16, type T = int, T x = 0)

( ... );

...

endmodule

WITH

The parameter keyword can be omitted in a parameter port list. For example:

class vector #(size = 1); // size is a parameter in a parameter port list

logic [size-1:0] v;

endclass

interface simple_bus #(AWIDTH = 64, type T = word) // parameter port list

(input bit clk) ; // port list

...

endinterface

In a list of parameter constants, a parameter can depend on earlier parameters. In the following declaration, the default value of the second parameter depends on the value of the first parameter. The third parameter is a type, and the fourth parameter is a value of that type.

module mc #(int N = 5, M = N*16, type T = int, T x = 0)

( ... );

...

endmodule

In the declaration of a parameter in a parameter_port_list, the specification for its default value may be omitted, in which case the parameter shall have no default value. If no default value is specified for a parameter of a design element, then the parameter shall be overridden in every instantiation of the design element (see 22.9). If a parameter of a design element has no default value, then the design element shall not be implicitly instantiated (see 22.3, 22.4, and 23.3). If no default value is specified for a parameter of a class, then the parameter shall be overridden in every specialization of the class (see 8.24).

class Mem #(type T, int size);

T words[size];

...

endclass

typedef Mem#(byte, 1024) Kbyte;

In 6.20.1, REPLACE

If any param_assignments appear in a parameter_port_list, then any param_assignments that appear within the module, interface, program or class shall become local parameters and shall not be overridden by any method.

WITH

If the declaration of a design element or class uses any param_assignments appear in a parameter_port_list (even an empty one), then any param_assignments that appear in any parameter_declaration directly contained within the module, interface, program or class declaration shall become local parameters and shall not be overridden by any method the parameter keyword shall be a synonym for the localparam keyword (see 6.20.4).