怎样消除 61061045 WARNING – The SN pin is not available for use as a general purpose I/O pin when the SLAVE_SPI_PORT attribute is enabled.

我发现我的XO3工程中有个警告，不知道如何消除，好像是不能分配引脚，望哪位大神能指导下。谢谢！

61061045 WARNING – The SN pin is not available for use as a general purpose I/O pin when the SLAVESPIPORT attribute is enabled. The SN pin should be tied high with an external pull-up if you are not using the Slave SPI port for configuration.