73. SR Latch

module sr_latch_nor (
    input  S,
    input  R,
    output reg Q,
    output reg Qn
);
    always @(*) begin
        case ({S,R})
            2'b00: begin
                Q  = Q;
                Qn = Qn;
            end
            2'b01: begin
                Q  = 1'b0;
                Qn = 1'b1;
            end
            2'b10: begin
                Q  = 1'b1;
                Qn = 1'b0;
            end
            2'b11: begin
                Q  = 1'b0;
                Qn = 1'b1;
            end
        endcase
    end
endmodule