How to Write Verilog Code for a Custom Counting Sequence 12345678 and Repeat

Verilog is a powerful hardware description language used to design digital electronics. Writing Verilog code for specific tasks, such as creating a counting sequence, is a fundamental skill for any software engineer or hardware designer. In this article, we will walk through the process of writing Verilog code for a custom counting sequence from 1 to 8, and then repeating the sequence. We will explore two methods: using a counter and utilizing a finite state machine (FSM).

Introduction to Verilog Code Writing

Before diving into the code, it's important to understand the basics of Verilog. Verilog is composed of tasks, modules, and statements that allow you to describe the behavior of digital circuits. In Verilog, you can use conditional statements, loops, and various constructs to manipulate data and control the flow of the design.

Method 1: Using a Counter

One way to achieve the desired sequence is by using a simple counter. The counter will increment from 1 to 8 and then reset to 1 when it reaches 8, repeating the sequence.

module custom_count(
    input wire clk,
    input wire reset,
    output reg [3:0] count
);
    always @(posedge clk or posedge reset)
    begin
        if (reset)
        begin
            count 

In this module, custom_count has a clock input clk and a reset input reset. The count output is a 4-bit register that holds the current value of the counter. The always block is triggered on the positive edge of the clk or reset signal. When reset is asserted, the counter is cleared to 0. Otherwise, if the counter reaches 7, it resets back to 0, thereby repeating the sequence.

Method 2: Using a Finite State Machine (FSM)

A finite state machine (FSM) is another effective way to implement the custom counting sequence. In an FSM, you move through a series of states based on transitions defined by input signals and internal conditions. This method can be more efficient and easier to understand for larger or more complex sequences.

module custom_count_fsm(
    input wire clk,
    input wire reset,
    output reg [3:0] count
);
parameter IDLE  0, COUNT_1_7  1, COUNT_8  2;
reg [1:0] current_state, next_state;
always @(posedge clk or posedge reset)
begin
    if (reset)
    begin
        current_state  IDLE;
        count  0;
    end
    else
    begin
        current_state  next_state;
    end
end
always @(current_state or count)
begin
    unique case (current_state)
        IDLE: next_state  COUNT_1_7;
        COUNT_1_7: begin
            if (count  7)
                next_state  COUNT_8;
            else
                next_state  COUNT_1_7;
        end
        COUNT_8: begin
            count  0;
            next_state  COUNT_1_7;
        end
    endcase
end
endmodule

This module, custom_count_fsm, uses a 2-bit current_state and next_state to manage transitions. The IDLE state initializes the count, then transitions to COUNT_1_7 and COUNT_8 as needed. When the count reaches 7, it transitions to COUNT_8 and resets the count to 0, repeating the sequence.

Conclusion

Both methods described above are effective for implementing a custom counting sequence from 1 to 8 and repeating it. The counter method is straightforward and easy to implement, while the FSM method offers more flexibility and scalability for more complex sequences. Whether you are a beginner or an experienced Verilog coder, understanding these techniques will help you write more efficient and robust hardware designs.

Keywords: Verilog coding, Verilog counter, Verilog finite state machine (FSM)