nRF24LE1 Nordic VLSI, nRF24LE1 Datasheet - Page 28

• Manufacturer Part Number: nRF24LE1
• Manufacturer: Nordic VLSI

nRF24LE1 Preliminary Product Specification
3.4.6
Enhanced ShockBurst™ features two functions for automatic packet transaction handling; auto acknowl-
edgement and auto re-transmit.
3.4.6.1
Auto acknowledgment is a function that automatically transmits an ACK packet to the PTX after it has
received and validated a packet. The auto acknowledgement function reduces the load of the system MCU
and reduces average current consumption. The Auto Acknowledgement feature is enabled by setting the
EN_AA register.
An ACK packet can contain an optional payload from PRX to PTX. In order to use this feature, the
Dynamic Payload Length (DPL) feature must be enabled. The MCU on the PRX side has to upload the
payload by clocking it into the TX FIFO by using the W_ACK_PAYLOAD command. The payload is pending
in the TX FIFO (PRX) until a new packet is received from the PTX. The RF Transceiver can have three
ACK packet payloads pending in the TX FIFO (PRX) at the same time.
Figure 11.
the MCU the payload is clocked in with the W_ACK_PAYLOAD command. The address decoder and buffer
controller ensure that the payload is stored in a vacant slot in the TX FIFO (PRX). When a packet is
received, the address decoder and buffer controller are notified with the PTX address. This ensures that
the right payload is presented to the ACK generator.
If the TX FIFO (PRX) contains more than one payload to a PTX, payloads are handled using the first in –
first out principle. The TX FIFO (PRX) is blocked if all pending payloads are addressed to a PTX where the
link is lost. In this case, the MCU can flush the TX FIFO (PRX) by using the FLUSH_TX command.
In order to enable Auto Acknowledgement with payload the EN_ACK_PAY bit in the FEATURE register
must be set.
3.4.6.2
The auto retransmission is a function that retransmits a packet if an ACK packet is not received. It is used
in an auto acknowledgement system on the PTX. When a packet is not acknowledged, you can set the
number of times it is allowed to retransmit by setting the ARC bits in the SETUP_RETR register. PTX enters
RX mode and waits a time period for an ACK packet each time a packet is transmitted. The amount of time
the PTX is in RX mode is based on the following conditions:
Revision 1.1
Note: If the received packet has the NO_ACK flag set, auto acknowledgement is not executed.
generator
shows how the TX FIFO (PRX) is operated when handling pending ACK packet payloads. From
Automatic packet transaction handling
ACK
Auto Acknowledgement
Auto Retransmission (ART)
RX Pipe
address
Figure 11. TX FIFO (PRX) with pending payloads
Address decoder and buffer controller
Payload 3
Payload 2
Payload 1
TX FIFO
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TX Pipe
address
Module
SPI
From
MCU