    def check_valid(self):
        self.raddr.wr(self.LSR);
        self.i_rx_en.wr(1);
        clkfence()

        self.i_rx_en.wr(0);
        clkfence()

        status = self.rdata.rd()
        rx_ready = 1 if ((status & 0x01) == 0x01) else 0
        clkfence()

        return rx_ready