attribute altera_attribute : string;
    attribute altera_attribute of x1 : signal is "-name IO_STANDARD ""2.5 V""";
    attribute altera_attribute of x2 : signal is "-name IO_STANDARD ""2.5 V""";
    attribute altera_attribute of pba : signal is "-name IO_STANDARD ""2.5 V""";
    attribute altera_attribute of pbb : signal is "-name IO_STANDARD ""2.5 V""";
    attribute altera_attribute of led : signal is "-name IO_STANDARD ""2.5 V""; -name CURRENT_STRENGTH_NEW 4MA";

    attribute chip_pin : string;
    attribute chip_pin of x1: signal is "88,89,90,91";
    attribute chip_pin of x2: signal is "49,46,25,24";
    attribute chip_pin of pba: signal is "64";
    attribute chip_pin of pbb: signal is "58";
    attribute chip_pin of led: signal is "65,66,67,68,69,70,71,72";