User defined types are same as that found in other programming language and same as found in C language. Using this, a user can define his own data types. A type can be used before it is defined, provided it is first identified as a type by an empty typedef:

Syntax

• typedef data_type type_identifier variable_dimension
• typedef interface_instance_identifier . type_identifier;
• typedef [ enum | struct | union | class ] type_identifier ;

Sometimes a user defined type needs to be declared before the contents of the type has been defined. This is of use with user defined types derived from enum, struct, union, and class.

• typedef enum type_declaration_identifier;
• typedef struct type_declaration_identifier;
• typedef union type_declaration_identifier;
• typedef class type_declaration_identifier;
• typedef type_declaration_identifier;

  1 `timescale 1ns/10ps
  2 
  3 // Type define a struct
  4 typedef struct {
  5   byte a;
  6   reg  b;
  7   shortint unsigned c;
  8 } myStruct;
  9 
 10 module typedef_data ();
 11 
 12 // Full typedef here
 13 typedef integer myinteger;
 14 
 15 // Typedef declaration without type
 16 typedef myinteger;
 17 // Typedef used here
 18 myinteger a = 10;
 19 myStruct object = '{10,0,100};
 20 
 21 initial begin
 22   $display ("a = %d", a);
 23   $display ("Displaying object");
 24   $display ("a = %b b = %b c = %h", object.a, object.b, object.c);
 25    #1  $finish;
 26 end
 27 
 28 endmodule

 a =          10
 Displaying object
 a = 00001010 b = 0 c = 0064

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Deepak Kumar Tala - All rights reserved

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