S24C16_do_bit
S24C16_do_bit(np, NULL, write_bit, gpreg);
S24C16_do_bit(np, read_bit, 1, gpreg);
S24C16_do_bit(np, NULL, (write_data >> (7 - x)) & 0x01, gpreg);
S24C16_do_bit(np, &read_bit, 1, gpreg);