📌 Introduction

Simple Explain: Latch vs Flip-Flop

  • Latch (Level-sensitive) 
    Enable=1 → Q = D  
Enable=0 → Q maintain
  • Flip-Flop (Edge-triggered) 
    CLK posedge → Q ← D  
Other times Q maintain

Latch in Verilog

always @(*) begin
    if (en)
        q = d;   // No else, q will maintain when en=0, thus build a latch.
end

🧑‍💻 Code Example

module top_module (
    input      cpu_overheated,
    output reg shut_off_computer,
    input      arrived,
    input      gas_tank_empty,
    output reg keep_driving  ); //

    always @(*) begin
        if (cpu_overheated)
           shut_off_computer = 1;
        else 
           shut_off_computer = 0;
    end

    always @(*) begin
        if (~arrived)
           keep_driving = ~gas_tank_empty;
        else
           keep_driving = 0;
    end

endmodule

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📚 Reference