CODEWITHSUNDEEP
system-verilog
nachum
nachum

Reputation: 567

localparam of struct type - using default values - still requires initializer?

Should a localparam of a struct type still require an initializer if it has default initial values?

Eg

typedef struct {
 int a = 1;
} my_struct;

localparam my_struct m;

Upvotes: 2

Views: 776

Answers (3)

Vladyslav Datsii
Vladyslav Datsii

Reputation: 17

This trick is supported in ModelSim (Intel) and synthesizable in Efinix. But using a function to partially override parameter values would be a bit awkward.

//define:
typedef struct  {
    bit PARAM1 = 1;
    bit PARAM2 = 0;
}some_localparameter_t;

function automatic some_localparameter_t SOME_LOCALPARAMETER_INIT();
    automatic some_localparameter_t P;
    return P;
endfunction

//example to use inside module declaration:
localparam some_localparameter_t SOME_LOCALPARAMETER = SOME_LOCALPARAMETER_INIT();

Upvotes: 0

dave_59
dave_59

Reputation: 42738

SystemVerilog syntax/semantics requires a declaration assignment for any localparam declaration, or a parameter declaration outside the module header (i.e. inside the module body).

Upvotes: 0

toolic
toolic

Reputation: 62236

Your code generates a syntax error on 3 major Verilog simulators. From IEEE Std 1800-2017, section 6.20.1 Parameter declaration syntax:

It shall be legal to omit the constant_param_expression from a param_assignment or the data_type from a type_assignment only within a parameter_port_list.

Upvotes: 0

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