analog.com interface spi_master_rtl 1.0 SCLK SPI clock required 1 out required 1 in SDI Serial data in optional in optional out 0 SDO Serial data out optional 1 out optional 1 in 0 SDO_T Serial data out three state controle line optional 1 out optional 1 in 0 THREE_WIRE Three wire mode optional 1 out optional 1 in 0 CS Chip select required out required in 0