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CC112X/CC1175
SWRU295C
Page 63 of 108
8.8
RC Oscillator Calibration
The frequency of the low-power RC oscillator used for the eWOR functionality varies with temperature
and supply voltage. In order to keep the frequency as accurate as possible, the RC oscillator should
be calibrated whenever possible. Two automatic RC calibration options are available that are
controlled by the
RC calibration is enabled when the XOSC is running
RC calibration is enabled on every 4th time the device is powered up and goes from IDLE to RX
(should only be used together with eWOR).
During calibration the eWOR timer will be clocked on a down-divided version of the XOSC clock.
When the chip goes to the SLEEP state, the RC oscillator will use the last valid calibration result. The
frequency of the RC oscillator is calibrated to the main crystal frequency divided by 1000.
In applications where the radio wakes up very often, typically several times every second, it is
possible to do the RC oscillator calibration once and then turn off calibration to reduce the current
consumption. If the RC oscillator calibration is turned off, it will have to be manually turned on again to
resume calibration. This will be necessary if temperature and supply voltage changes to maintain
accuracy.
setting is altered from 00b or 01b to 10b or 11b (enabled), an
command strobe must be issued before the new configuration is taken into account. If it is altered
from 10b or 11b to 00b or 01b (disabled), and
, or
When not using eWOR and RC calibration is enabled, staying in TX or RX mode over a long period of
time will cause internal heating of the chip, which again might cause the RC OSC period to increase.
It is therefore recommended to turn off RCOSC calibration during active mode.
8.9
Antenna Diversity and
Multiple Path Transmission
CC112X
has two different antenna diversity modes: Single-switch mode and continuous-switch mode.
Single switch mode is useful for very low power schemes where the device only checks each antenna
once for a signal and directly returns to power down if a signal is not detected (automated using the
eWOR feature). If a signal is found on the first antenna checked, it does not check the second
antenna.
Continuous mode is useful when staying in RX for longer intervals.
The antenna diversity algorithm can operate based on PQT or CS. The user can configure how the
device will act in regards to antenna diversity and RX termination as described in Table 28.
Table 28:
RFEND_CFG0.ANT_DIV_RX_TERM_CFG
Setting
RFEND_CFG0.
ANT_DIV_RX_TERM_CFG
Description
000
Antenna diversity and termination based on CS/PQT are disabled
001
RX termination base on CS is enabled (Antenna diversity OFF). See 8.5.2 for details.
010
Single-switch antenna diversity on CS enabled.
One or both antenna is CS evaluated once and RX will terminate if CS failed on both
antennas.
011
Continuous-switch antenna diversity on CS enabled.
Antennas are switched until CS is asserted or RX timeout occurs (if RX timeout is enabled)
100
RX termination base on PQT is enabled (Antenna diversity OFF). See 8.5.3 for details.
101
Single-switch antenna diversity on PQT enabled.
One or both antenna is PQT evaluated once and RX will terminate if PQT is not reached on
any of the antennas.
110
Continuous-switch antenna diversity on PQT enabled.
Antennas are switched until PQT is reached or RX timeout occurs (if RX timeout is enabled)
111
Reserved