14.1.3.1 Register Access Mode
Register Access Mode is used to read and write AT86RF212B registers (register address from 0x00 up to 0x3F).
A register access mode is a two-byte read/write operation initiated by /SEL = L. The first transferred byte on MOSI is the command byte including an identifier bit (bit[7] = 1), a read/write select bit (bit[6]), and a 6-bit register address.
On read access, the content of the selected register address is returned in the second byte on MISO.
On write access, the second byte transferred on MOSI contains the write data to the selected address.
Each register access must be terminated by setting /SEL = H.
The figure below illustrates a typical SPI sequence for a register access sequence for write and read respectively.