module inpad(
    output Q,
    (* iopad_external_pin *)
    input P
);
    assign Q = P;
endmodule

module outpad(
    (* iopad_external_pin *)
    output P,
    input A
);
    assign P = A;
endmodule

module ckpad(
    output Q,
    (* iopad_external_pin *)
    input P
);
    assign Q = P;
endmodule

module bipad(
    input A,
    input EN,
    output Q,
    (* iopad_external_pin *)
    inout P
);
    assign Q = P;
    assign P = EN ? A : 1'bz;
endmodule


module dff(
    output reg Q,
    input D,
    (* clkbuf_sink *)
    input CLK
);
    parameter [0:0] INIT = 1'b0;
    initial Q = INIT;
    always @(posedge CLK)
        Q <= D;
endmodule