📌 Introduction

  • The case statement begins with case and each “case item” ends with a colon. There is no “switch”.
  • Each case item can execute exactly one statement. This makes the “break” used in C unnecessary. But this means that if you need more than one statement, you must use begin ... end.
  • Duplicate (and partially overlapping) case items are permitted. The first one that matches is used. C does not allow duplicate case items.

🧑‍💻 Code Example - 6-to-1 multiplexer

module top_module ( 
    input [2:0] sel, 
    input [3:0] data0,
    input [3:0] data1,
    input [3:0] data2,
    input [3:0] data3,
    input [3:0] data4,
    input [3:0] data5,
    output reg [3:0] out   );

    always@(*) begin  // This is a combinational circuit
        case(sel)
            3'b000: out = data0;
            3'b001: out = data1;
            3'b010: out = data2;
            3'b011: out = data3;
            3'b100: out = data4;
            3'b101: out = data5;
            default: out = 3'b0;
        endcase
    end

endmodule

📚 Reference