Can someone kindly explain what are SPI_CS1 (e.g. DIO1), SPI_CS2 (e.g. DIO18), and SPI_CS3 (e.g. DIO19) on BlueNRG-2?

[MAmiri]

As far as I have understood, CS2 can be used for BlueNRG-2 acting as master and the another chip in salve mode, I can also see CS1 pin is also used for JTAG operation, does this mean CS1 can place BlueNRG-2 in slave mode for SPI communications? What about SPI_CS3?

And finally how to use them?

Thanks!