82. JK Flip-Flop with Enable

module jk_ff_enable (
    input  CLK,
    input  EN,
    input  J,
    input  K,
    output reg Q
);
    always @(posedge CLK) begin
        if (EN) begin
            case ({J, K})
                2'b00: Q <= Q;       // hold
                2'b01: Q <= 1'b0;    // reset
                2'b10: Q <= 1'b1;    // set
                default: Q <= ~Q;    // toggle
            endcase
        end
    end
endmodule

💡Remember

• EN masks the JK function; when low, the state is retained regardless of J/K.
• Synthesizers usually implement JK as logic feeding a D flip-flop; writing it directly with a clocked case is clear and portable.
• Nonblocking assignments (<=) ensure the toggle uses the pre-edge value of Q and avoid races across sequential paths.