The state diagram (Figure 3.) shows the modes the nRF24L01 can operate in and how they are accessed.
The nRF24L01 is undefined until the VDD becomes 1.9V or higher. When this happens nRF24L01 enters
the Power on reset state where it remains in reset until it enters the Power Down mode. Even when the
nRF24L01 enters Power Down mode the MCU can control the chip through the SPI and the Chip Enable
(CE) pin Three types of states are used in the state diagram. “Recommended operating mode” is a state
that is used during normal operation. “Possible operating mode” is a state that is allowed to use, but it is
not used during normal operation. “Transition state” is a time limited state used during start up of the oscillator
and settling of the PLL.