CC2420-RTR1 datasheet(34/92 Pages) TI

34 / 92 page

CC2420

SWRS041B

Page 34 of 89

Preamble

SFD Length

Data received over RF

SFD Pin

FIFO Pin

FIFOP Pin, if threshold

higher than frame length

FIFOP Pin, if threshold

lower than frame length

cte

ive

Preamble

SFD Length

Data received over RF

SFD Pin

FIFO Pin

FIFOP Pin

s r

nit

ion

ple

MAC Protocol Data Unit (MPDU) with correct address

MAC Protocol Data Unit (MPDU) with wrong address

Address

recognition OK

Address

recognition fails

Figure 13. Pin activity examples during receive

ADDR

TXFIFO

PSDU0

PSDU1

Length

Status

PSDU5

PSDU2

PSDU3

RSSI

CSn

SFD

SCLK

FIFOP

FIFO

PSDU4

low

t o

f la

sta

rts

ain

hig

lon

r o

s >

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

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.

CC2420-RTR1 数据表(PDF) 34 Page - Texas Instruments

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