RF70 Datasheet, PDF (11/25 Pages) –

IRQ to MCU. Two packet loss counters
(ARC_CNT and PLOS_CNT) are incremented
each time a packet is lost. The ARC_CNT
counts the number of retransmissions for the
current transaction. The PLOS_CNT counts
the total number of retransmissions since the
last channel change. ARC_CNT is reset by
initiating a new transaction. PLOS_CNT is
reset by writing to the RF_CH register. It is
possible to use the information in the
OBSERVE_TX register to make an overall
assessment of the channel quality.
The PTX device will retransmit if its RX FIFO
is full but received ACK frame has payload.
As an alternative for PTX device to auto
retransmit it is possible to manually set the
RF70 to retransmit a packet a number of times.
This is done by the REUSE_TX_PL command.
When auto acknowledge is enabled, the PRX
device will automatically check the NO_ACK
field in received packet, and if NO_ACK=0, it
will automatically send an acknowledge
packet to PTX device. If EN_ACK_PAY is set,
and the acknowledge packet can also include
pending payload in TX FIFO.
6 Data and Control Interface
6.1 TX/RX FIFO
The data FIFOs are used to store payload that
is to be transmitted (TX FIFO) or payload that
is received and ready to be clocked out (RX
FIFO). The FIFO is accessible in both PTX
mode and PRX mode.
There are three levels 32 bytes FIFO for both
TX and RX, supporting both acknowledge
mode or no acknowledge mode with up to six
pipes.
 TX three levels, 32 byte FIFO
 RX three levels, 32 byte FIFO
Both FIFOs have a controller and are
RF70 V1.0
accessible through the SPI by using dedicated
SPI commands. A TX FIFO in PRX can store
payload for ACK packets to three different
PTX devices. If the TX FIFO contains more
than one payload to a pipe, payloads are
handled using the first in first out principle.
The TX FIFO in a PRX is blocked if all
pending payloads are addressed to pipes where
the link to the PTX is lost. In this case, the
MCU can flush the TX FIFO by using the
FLUSH_TX command.
The RX FIFO in PRX may contain payload
from up to three different PTX devices.
.
A TX FIFO in PTX can have up to three
payloads stored.
The TX FIFO can be written to by three
commands, W_TX_PAYLOAD and
W_TX_PAYLOAD_NO_ACK in PTX mode
and W_ACK_PAYLOAD in PRX mode. All
three commands give access to the TX_PLD
register.
The RX FIFO can be read by the command
R_RX_PAYLOAD in both PTX and PRX
mode. This command gives access to the
RX_PLD register.
The payload in TX FIFO in a PTX is NOT
removed if the MAX_RT IRQ is asserted.
In the FIFO_STATUS register it is possible to
read if the TX and RX FIFO are full or empty.
The TX_REUSE bit is also available in the
FIFO_STATUS register. TX_REUSE is set by
the SPI command REUSE_TX_PL, and is
reset by the SPI command:
W_TX_PAYLOAD or FLUSH TX.
6.2 Interrupt
In RF70 there is an active low interrupt (IRQ)
pin, which is activated when TX_DS IRQ,
RX_DR IRQ or MAX_RT IRQ are set high by
the state machine in the STATUS register. The
IRQ pin resets when MCU writes
'1' to the IRQ source bit in the STATUS
register. The IRQ mask in the CONFIG
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