User Manual

Revision 1.0 Page 36 of 78
nRF24L01+ Product Specification
Activate PTX mode by setting the CE pin high. If there is a packet present in the TX FIFO the nRF24L01+
enters TX mode and transmits the packet. If Auto Retransmit is enabled, the state machine checks if the
NO_ACK flag is set. If it is not set, the nRF24L01+ enters RX mode to receive an ACK packet. If the
received ACK packet is empty, only the TX_DS IRQ is asserted. If the ACK packet contains a payload,
both TX_DS IRQ and RX_DR IRQ are asserted simultaneously before nRF24L01+ returns to standby-I
mode.
If the ACK packet is not received before timeout occurs, the nRF24L01+ returns to standby-II mode. It
stays in standby-II mode until the ARD has elapsed. If the number of retransmits has not reached the ARC,
the nRF24L01+ enters TX mode and transmits the last packet once more.
While executing the Auto Retransmit feature, the number of retransmits can reach the maximum number
defined in ARC. If this happens, the nRF24L01+ asserts the MAX_RT IRQ and returns to standby-I mode.
If the CE is high and the TX FIFO is empty, the nRF24L01+ enters Standby-II mode.