Posedge Verilog?

Question

What is posedge in Verilog, and how do I use it?

Answer 1

The posedge is the event of changing a value of either a variable or net with a direction toward the value 1. The posedge is detected on the transition from 0 to (x, z, or 1), and from (x or z) to 1. I use it to define either a flip-flop or a flip-flop with an asynchronous reset in a sequential logic.

always @(posedge clk) q <= d;
always @(posedge clk or negedge reset_n) begin
    if (!reset_n) q <= 1'b0;
    else q <= d;
end

Answer 2

posedge means that the block will trigger on the rising (positive) edge of the clock. The syntax is:

always @(posedge clk) begin
// codes here
end

This means that when there is a rising edge of signal 'clk', the code inside the begin-end statement will execute. Another way to use poseedge is:

@(posedge clk);
// code2 here

The above given code means that the statements in 'code2' will not execute until a positive edge of 'clk' occurs.