Vectors

What is vectors?

Vectors are used to group related signals using one name to make it more convenient to manipulate. For example, wire [7:0] w; declares an 8-bit vector named w that is functionally equivalent to having 8 separate wires.

Notice that the declaration of a vector places the dimensions before the name of the vector, which is unusual compared to C syntax. However, the part select has the dimensions after the vector name as you would expect.

Example:

wire [99:0] my_vector;      // Declare a 100-element vector
assign out = my_vector[10]; // Part-select one bit out of the vector

Problem statement

Build a circuit that has one 3-bit input, then outputs the same vector, and also splits it into three separate 1-bit outputs. Connect output o0 to the input vector's position 0, o1 to position 1, etc.

Notice:In a diagram, a tick mark with a number next to it indicates the width of the vector (or "bus"), rather than drawing a separate line for each bit in the vector.

module top_module ( 
    input wire [2:0] vec,
    output wire [2:0] outv,
    output wire o2,
    output wire o1,
    output wire o0  ); // Module body starts after module declaration

endmodule

Solution

module top_module ( 
    input wire [2:0] vec,
    output wire [2:0] outv,
    output wire o2,
    output wire o1,
    output wire o0  ); // Module body starts after module declaration
    assign outv=vec,o0=vec[0],o1=vec[1],o2=vec[2];
    //  This is ok too: assign {o2, o1, o0} = vec;
endmodule