In order to request ownership of the common SPI bus, bit 7 of the register must be set ('1'). The register must also be loaded with the address of the device to which you wish to communicate. This address must be stored in bits 4..0 of the register. For device addresses, see Selecting a Slave SPI Device.
Data transfer on the SPI bus is always MSB first. The 8-bit value you intend to load into the address register is shifted into the register from the
SPI_DOUT line, one bit at a time (from the right), on each rising edge of the
SPI_CLK signal. For example, if you are using a NanoBoard NB2, and wish to request bus ownership in order to talk to the Touch Screen Digitizer, with address
00101, you must send out the 8 bit value
1xx00101 on the