CC1110Fx / CC1111Fx
Carrier Sense can be used as a sync word
qualifier that requires the signal level to be
higher than the threshold for a sync word
search to be performed. The signal can also
be observed on P1_5, P1_6, or P1_7 by
setting IOCFGx.GDOx_CFG=1110 and in the
status register bit PKTSTATUS.CS.
MAX_DVGA_GAIN[1:0]
00
01
10
11
000
001
010
011
100
101
110
111
–99
–93
–87
–85
–82
–80
–78
–76
–73
–70
–81.5
–78.5
–76
–97
–90.5
–87
–93.5
–91.5
–90.5
–88
–86
–74
Other uses of Carrier Sense include the TX-if-
CCA function (see Section 13.10.7 on Page
201) and the optional fast RX termination (see
Section 13.12.3 on Page 205).
–84
–72.5
–70
–82.5
–78.5
–76
–84.5
–82.5
–67
CS can be used to avoid interference from
other RF sources in the ISM bands.
–64
Table 69: Typical RSSI Value in dBm at CS
Threshold with Default MAGN_TARGETat 2.4
kBaud
13.10.5 CS Absolute Threshold
The absolute threshold related to the RSSI
value depends on the following register fields:
MAX_DVGA_GAIN[1:0]
AGCCTRL2.MAX_LNA_GAIN
AGCCTRL2.MAX_DVGA_GAIN
00
01
10
11
000
001
010
011
100
101
110
111
–96
–90
–89
–87
–85
–82
–79.5
–76.5
–72
–84
–78.5
–77.5
–75
–94.5
–92.5
–91
–83
AGCCTRL1.CARRIER_SENSE_ABS_THR
AGCCTRL2.MAGN_TARGET
–81
–78.5
–76
–73
For a given AGCCTRL2.MAX_LNA_GAIN and
–87.5
–85
–70
AGCCTRL2.MAX_DVGA_GAIN
absolute threshold can be adjusted ±7 dB in
steps of dB using
CARRIER_SENSE_ABS_THR.
setting
the
–73.5
–70.5
–66
–67.5
–65
1
–83
–78
–60
The MAGN_TARGET setting is a compromise
between blocker tolerance/selectivity and
sensitivity. The value sets the desired signal
level in the channel into the demodulator.
Increasing this value reduces the headroom for
blockers, and therefore close-in selectivity. It is
strongly recommended to use SmartRF®
Table 70: Typical RSSI Value in dBm at CS
Threshold with Default MAGN_TARGETat 250
kBaud
If the threshold is set high, i.e. only strong
signals are wanted, the threshold should be
adjusted upwards by first reducing the
Studio
[9]
to
generate
the
correct
MAGN_TARGET setting. Table 69 and Table 70
show the typical RSSI readout values at the
CS threshold at 2.4 kBaud and 250 kBaud
MAX_LNA_GAIN
value
and
then
the
MAX_DVGA_GAIN value. This will reduce
power consumption in the receiver front end,
since the highest gain settings are avoided.
data
rate
respectively.
The
default
CARRIER_SENSE_ABS_THR=0 (0 dB) and
MAGN_TARGET=11(33 dB) have been used.
13.10.6 CS Relative Threshold
For other data rates the user must generate
similar tables to find the CS absolute
threshold.
The relative threshold detects sudden changes
in the measured signal level. This setting is not
dependent on the absolute signal level and is
thus useful to detect signals in environments
with a time varying noise floor. The register
field AGCCTRL1.CARRIER_SENSE_REL_THR
is used to enable/disable relative CS, and to
select threshold of 6 dB, 10 dB or 14 dB RSSI
change
SWRS033H
Page 200 of 246
TI [ TEXAS INSTRUMENTS ]
