nRF24LE1 Nordic VLSI, nRF24LE1 Datasheet - Page 29

• Manufacturer Part Number: nRF24LE1
• Manufacturer: Nordic VLSI

nRF24LE1 Preliminary Product Specification
The RF Transceiver asserts the TX_DS IRQ when the ACK packet is received.
The RF Transceiver enters standby-I mode if there is no more untransmitted data in the TX FIFO and the
rfce bit in the RFCON register is low. If the ACK packet is not received, the RF Transceiver goes back to
TX mode after a delay defined by ARD and retransmits the data. This continues until acknowledgment is
received, or the maximum number of retransmits is reached.
Two packet loss counters are incremented each time a packet is lost, ARC_CNT and PLOS_CNT in the
OBSERVE_TX register. The ARC_CNT counts the number of retransmissions for the current transaction.
You reset ARC_CNT by initiating a new transaction. The PLOS_CNT counts the total number of retrans-
missions since the last channel change. You reset PLOS_CNT by writing to the RF_CH register. It is possi-
ble to use the information in the OBSERVE_TX register to make an overall assessment of the channel
quality.
The ARD defines the time from the end of a transmitted packet to when a retransmit starts on the PTX.
ARD is set in SETUP_RETR register in steps of 250µs. A retransmit is made if no ACK packet is received by
the PTX.
There is a restriction on the length of ARD when using ACK packets with payload. The ARD time must
never be shorter than the sum of the startup time and the time on-air for the ACK packet.
ARD=500µs is long enough for any ACK payload length in 1 or 2Mbps mode.
As an alternative to Auto Retransmit it is possible to manually set the RF Transceiver to retransmit a
packet a number of times. This is done by the REUSE_TX_PL command. The MCU must initiate each
transmission of the packet with a pulse on the CE pin when this command is used.
Revision 1.1
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Auto Retransmit Delay (ARD) elapsed.
No address match within 250µs.
After received packet (CRC correct or not) if address match within 250µs.
For 2Mbps data rate and 5 byte address; 15 byte is maximum ACK packet payload length for
For 1Mbps data rate and 5 byte address; 5 byte is maximum ACK packet payload length for
ARD=250µs (reset value).
For 250kbps data rate and 5byte address the following values apply:
ARD=250µs (reset value).
Table 6. Maximum ACK payload length for different retransmit delays at 250kbps
1500µs
1250µs
1000µs
750µs
500µs
ARD
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ACK packet size (in bytes)
Empty ACK with no payload
All ACK payload sizes
< 24
< 16
< 8