CC2400_07 Datasheet, PDF (45/83 Pages) Texas Instruments – 2.4 GHz Low-Power RF Transceiver

CC2400
35 Carrier Sense
The carrier sense signal is based on the
measured RSSI value and a
programmable threshold. The carrier-
sense function can be used to simplify the
implementation of a CSMA (Carrier Sense
Multiple Access) medium access protocol.
Carrier sense threshold level is
programmed
by
RSSI.RSSI_CS_THRES[5:0].
The
value of this register can be calculated in
the same way as described for
RSSI.RSSI_VAL in the previous section,
except that the unit is 4 dB instead of 1
dB. The default level (0x3C) corresponds
to a threshold of –70 dBm. A threshold of
0x09 corresponds to –18 dBm, and a
threshold of 0x37 corresponds to –90
dBm.
The carrier sense signal can be
multiplexed to the GIO1/GIO6 pin. The
CARRIER_SENSE_N signal is enabled by
setting IOCFG.GIO1_CFG[5:0] =
01010B (see Table 18).
36 Interfacing an External LNA or PA
CC2400 has two digital output pins, GIO1
and GIO6, which can be used to control
an external LNA or PA. The functionality of
these pins are controlled through the
IOCFG register.
The PA_EN, PA_EN_N, RX_PD, TX_PD
signals can be multiplexed to the
GIO1/GIO6 pin and used for controlling
the PA / LNA and one or more T/R
switches.
These two pins can also be used as two
general control signals, see Table 18.
For further information on attaching a PA,
please see page 54.
37 General Purpose / Test Output Control Pins
The two digital output pins, GIO1 and
GIO6, can be used as two general control
signals
by
writing
to
IOCFG.GIO1_CFG[5:0]
and
IOCFG.GIO6_CFG[5:0].
GIO1_CFG = 61 sets the pin low, and
GIO1_CFG = 62 sets the pin high.
This feature can be used to save I/O pins
on the microcontroller when the other
functions associated with these pins are
not used.
These two pins can also be used as a test
pin to monitor a lot of internal signals. This
is summarized in Table 18.
GIO1_CFG /
GIO6_CFG
[decimal]
0
1
2
3
4
5
6
7
8
9
Signal
Reserved
Reserved
Reserved
PA_EN
PA_EN_N
SYNC_RECEIVED
PKT
Reserved
Reserved
Reserved
I/O
Description
O
Reserved
O
Reserved
O
Reserved
O
Active high PA enable signal
O
Active low PA enable signal
O
Set if a valid sync word has been received since last
time RX was turned on
O
Packet status signal See Figure 10, page 28.
I
Reserved
O
Reserved
O
Reserved
SWRS042A
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