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Introduction
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SystemVerilog added lot of new data types and improved the existing data types to improve run time memory utilization of simulators. Highlights of the SystemVerilog datatypes are below |
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- shortint and longint data types.
- shortreal (real was already defined in Verilog) data type.
- string, chandle and class data types.
- logic, bit and byte data type.
- User defined types typedef.
- struct, union, and class data types.
- void data type.
- null data type.
- arrays, queue, associative array, dynamic array
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Next few pages we shall see the basics of this new data types, and then in later chapers we shall see the details of each of this data types. |
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Note : User define data types defined by typedef should be first defined before they are used. |
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Integer data types
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Integer data types can be classified into 2-state types and 4-state types. 2-state types can take only 0, 1, where as 4-state types can take 0,1,X,Z. 2-state types consume less (50%) memory and simulate faster when compared to 4-state types. |
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2 state value integer data types are |
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- shortint : 16-bit signed integer.
- int : 32-bit signed integer.
- longint : 64-bit signed integer.
- byte : 8-bit signed integer, can be used for storing ASCII charater.
- bit : User defined vector types.
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4-state value integers data types are |
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- logic : User defined vector types.
- reg : User defined vector types.
- wire : User defined vector types.
- integer : 32-bit signed integer.
- time : 64-bit unsigned integer.
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Integer types can be signed or unsigned, thus can change the result of a arthimetic operation. So care should be taken when declaring the data types that may be have to do arthimetic operation on it. By default byte, shortint, int, integer and longint default to signed and bit, reg, logic, and wire defaults to unsigned. |
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NoteData type reg and logic are one and same. logic data type was introduced to avoid confusion with reg data type. |
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Example - Integer Types
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1 module data_types();
2
3 bit data_1bit;
4 byte data_8bit;
5 shortint data_16bit;
6 int data_32bit;
7 longint data_64bit;
8 integer data_integer;
9
10 bit unsigned data_1bit_unsigned;
11 byte unsigned data_8bit_unsigned;
12 shortint unsigned data_16bit_unsigned;
13 int unsigned data_32bit_unsigned;
14 longint unsigned data_64bit_unsigned;
15 integer unsigned data_integer_unsigned;
16
17 initial begin
18 data_1bit = {32{4'b1111}};
19 data_8bit = {32{4'b1111}};
20 data_16bit = {32{4'b1111}};
21 data_32bit = {32{4'b1111}};
22 data_64bit = {32{4'b1111}};
23 data_integer= {32{4'b1111}};
24 $display("data_1bit = %0d",data_1bit);
25 $display("data_8bit = %0d",data_8bit);
26 $display("data_16bit = %0d",data_16bit);
27 $display("data_32bit = %0d",data_32bit);
28 $display("data_64bit = %0d",data_64bit);
29 $display("data_integer = %0d",data_integer);
30 data_1bit = {32{4'bzx01}};
31 data_8bit = {32{4'bzx01}};
32 data_16bit = {32{4'bzx01}};
33 data_32bit = {32{4'bzx01}};
34 data_64bit = {32{4'bzx01}};
35 data_integer= {32{4'bzx01}};
36 $display("data_1bit = %b",data_1bit);
37 $display("data_8bit = %b",data_8bit);
38 $display("data_16bit = %b",data_16bit);
39 $display("data_32bit = %b",data_32bit);
40 $display("data_64bit = %b",data_64bit);
41 $display("data_integer = %b",data_integer);
42 data_1bit_unsigned = {32{4'b1111}};
43 data_8bit_unsigned = {32{4'b1111}};
44 data_16bit_unsigned = {32{4'b1111}};
45 data_32bit_unsigned = {32{4'b1111}};
46 data_64bit_unsigned = {32{4'b1111}};
47 data_integer_unsigned = {32{4'b1111}};
48 $display("data_1bit_unsigned = %d",data_1bit_unsigned);
49 $display("data_8bit_unsigned = %d",data_8bit_unsigned);
50 $display("data_16bit_unsigned = %d",data_16bit_unsigned);
51 $display("data_32bit_unsigned = %d",data_32bit_unsigned);
52 $display("data_64bit_unsigned = %d",data_64bit_unsigned);
53 $display("data_integer_unsigned = %d",data_integer_unsigned);
54 data_1bit_unsigned = {32{4'bzx01}};
55 data_8bit_unsigned = {32{4'bzx01}};
56 data_16bit_unsigned = {32{4'bzx01}};
57 data_32bit_unsigned = {32{4'bzx01}};
58 data_64bit_unsigned = {32{4'bzx01}};
59 data_integer_unsigned = {32{4'bzx01}};
60 $display("data_1bit_unsigned = %b",data_1bit_unsigned);
61 $display("data_8bit_unsigned = %b",data_8bit_unsigned);
62 $display("data_16bit_unsigned = %b",data_16bit_unsigned);
63 $display("data_32bit_unsigned = %b",data_32bit_unsigned);
64 $display("data_64bit_unsigned = %b",data_64bit_unsigned);
65 $display("data_integer_unsigned = %b",data_integer_unsigned);
66 #1 $finish;
67 end
68
69 endmodule
You could download file data_types.sv here
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Simulation Output - Integer Types
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data_1bit = 1
data_8bit = -1
data_16bit = -1
data_32bit = -1
data_64bit = -1
data_integer = -1
data_1bit = 1
data_8bit = 00010001
data_16bit = 0001000100010001
data_32bit = 00010001000100010001000100010001
data_64bit = 0001000100010001000100010001000
100010001000100010001000100010001
data_integer = zx01zx01zx01zx01zx01zx01zx01zx01
data_1bit_unsigned = 1
data_8bit_unsigned = 255
data_16bit_unsigned = 65535
data_32bit_unsigned = 4294967295
data_64bit_unsigned = 18446744073709551615
data_integer_unsigned = 4294967295
data_1bit_unsigned = 1
data_8bit_unsigned = 00010001
data_16bit_unsigned = 0001000100010001
data_32bit_unsigned = 00010001000100010001000100010001
data_64bit_unsigned = 0001000100010001000100010001000
100010001000100010001000100010001
data_integer_unsigned = zx01zx01zx01zx01zx01zx01zx01zx01
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Copyright © 1998-2014 |
Deepak Kumar Tala - All rights reserved |
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Do you have any Comment? mail me at:deepak@asic-world.com
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