The Serial Peripheral Interface Bus or SPI bus is a synchronous serial data link standard named by Motorola that operates in full duplex mode. Devices communicate in a master/slave mode where the master device initiates the data frame. Multiple slave devices are allowed with individual slave select (chip select) lines using a pin for each device. The setBitOrder() method sets the bit order to use for SPI communication.
SPI.setBitOrder(order) SPI.setBitOrder(slaveSelectPin, order)(Arduino Due only)