The read and write functions represent the two different phases of the SPI transaction. Most SPI slave devices are capable of communicating using a full-duplex mechanism, so that bytes are exchanged in both directions while the clock is active. During each interval, a byte is transmitted in both directions, using the MISO and MOSI lines independently.
A common strategy, implemented by many slaves, consists of accessing registers for read and write operations in the slave devices, by using well-known command handles that are documented in the device's datasheet.
The STM32F407-Discovery board has an accelerometer connected to the SPI1 bus, which responds to predefined commands accessing specific registers in the device memory ...
