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Formal Definition

Vectors are multiple bit widths net or reg data type variables that can be declared by specifying their range.

Simplified Syntax

net_type [msb:lsb] list_of_net_identifiers;

reg [msb:lsb] list_of_register_identifiers;


Vector range specification contains two constant expressions: the msb (most significant bit) constant expression, which is the left-hand value of the range and the lsb (least significant bit) constant expression, which is the right-hand value of the range. The msb and lsb constant expressions should be separated by a colon.

Both the msb constant expression and the lsb constant expression can be any value - positive, negative, or zero. The lsb constant expression can be greater, equal or less than the msb constant expression.

Vectors can be declared for all types of net data types and for reg data types. Specifying vectors for integer, real, realtime, and time data types is illegal.

Vector nets and registers are treated as unsigned values (see: Arithmetic expressions with registers and integers for more explanations).


Example 1

reg [3:0] addr;

The 'addr' variable is a 4-bit vector register made up of addr[3] (the most significant bit), addr[2], addr[1], and addr[0] (the least significant bit).

Example 2

wire [-3:4] d;

The d variable is 8-bit vector net made up of d[-3] (msb), d[-2], d[-1], d[0], d[1], d[2], d[3], d[4] (lsb).

Example 3

tri [5:0] x, y, z;

The above line declares three 6-bit vectors.

Important Notes

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