Quartus II Project - notes [2]

Always / Initial Blocks (Procedural Assignments)

 

1. initial 

    - each 'initial' blocks executes concurrently starting at time 0.

    - executes only 'once' and does not execute again.

module system;

    reg a, b, c, d; // single statement
    
    initial a = 1'b0; // time 0 : power ON
    
    initial begin
        b = 1'b1;
        #5 c = 1'b0;
        #10 d = 1'b0;
    end
    
    initial #20 $finish;
    
endmodule

 

2. always

    - each 'always' blocks executes concurrently starting at time 0.

    - executes continuously in a looping fashion.

    - Modeling a digital circuits.

module clk_gen // 1. frequency 2. duty ratio 3. infinite
    #(parameter period = 50)
    (
    output reg clk
);
    initial clk = 1'b0;
    
    always
        #(period/2) clk = ~clk; // 0 = ~0, delay #25
    
    initial #100 $finish;
    
endmodule

 

Procedural Assignment Types.

 

1. Blocking

    - 

2. Non-Blocking