CC2420 Datasheet, PDF (34/92 Pages) List of Unclassifed Manufacturers – 2.4 GHz IEEE 802.15.4 / ZigBee-ready RF Transceiver

Data received over RF
Address
recognition OK
SFD Pin
FIFO Pin
FIFOP Pin, if threshold
higher than frame length
FIFOP Pin, if threshold
lower than frame length
Preamble
CC2420
SFD ^{detecteLdength byte received}
Adcdoremspsleretecdognition
SFD Length
MAC Protocol Data Unit (MPDU) with correct address
LasbtyMtePrDecUeived
Data received over RF
Address
recognition fails
SFD Pin
FIFO Pin
FIFOP Pin
Preamble
SFD Length
MAC Protocol Data Unit (MPDU) with wrong address
SCLK
SFD
CSn
SI
SO
FIFOP
FIFO
Figure 13. Pin activity examples during receive
FIFaOsPbloyrnteegmsaa>sinFnsIuFhmOigbPhe_rToHf ^R
ADDR_TXFIFO
Status
-
Length
-
PSDU0
-
PSDU1
-
PSDU2
-
PSDU3
-
PSDU4
-
PSDU5
FIFrOeasgdtoaoerutsst ^{olofwlawsthbeynte}
-
RSSI
-
FCS/Corr
Figure 14. Example of pin activity when reading RXFIFO.
14.4 Transmit mode
During transmit the FIFO and FIFOP pins
are still only related to the RXFIFO. The
SFD pin is however active during
transmission of a data frame, as shown in
Figure 15.
The SFD pin goes active when the SFD
field has been completely transmitted. It
goes inactive again when the complete
MPDU (as defined by the length field) has
been transmitted or if an underflow is
detected. See the RF Data Buffering
section on page 39 for more information
on TXFIFO underflow.
As can be seen from comparing Figure 13
and Figure 15, the SFD pin behaves very
similarly during reception and transmission
of a data frame. If the SFD pins of the
transmitter and the receiver are compared
during the transmission of a data frame, a
small delay of approximately 2 µs can be
seen because of bandwidth limitations in
both the transmitter and the receiver.
SWRS041B
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