Texas Instruments CC1101 User Manual

CC1101
SWRS061H Page 52 of 98
19.3 Voltage Regulator Control
The voltage regulator to the digital core is
controlled by the radio controller. When the
chip enters the SLEEP state which is the state
with the lowest current consumption, the
voltage regulator is disabled. This occurs after
CSn is released when a SPWD command
strobe has been sent on the SPI interface. The
chip is then in the SLEEP state. Setting CSn
low again will turn on the regulator and crystal
oscillator and make the chip enter the IDLE
state.
When Wake on Radio is enabled, the WOR
module will control the voltage regulator as
described in Section19.5.
19.4 Active Modes (RX and TX)
CC1101 has two active modes: receive and
transmit. These modes are activated directly
by the MCU by using the SRX and STX
command strobes, or automatically by Wake
on Radio.
The frequency synthesizer must be calibrated
regularly. CC1101 has one manual calibration
option (using the SCAL strobe), and three
automatic calibration options that are
controlled by the MCSM0.FS_AUTOCAL setting:
 Calibrate when going from IDLE to either
RX or TX (or FSTXON)
 Calibrate when going from either RX or TX
to IDLE automatically
3
 Calibrate every fourth time when going
from either RX or TX to IDLE
automatically
3
If the radio goes from TX or RX to IDLE by
issuing an SIDLE strobe, calibration will not be
performed. The calibration takes a constant
number of XOSC cycles; see Table 34 for
timing details regarding calibration.
When RX is activated, the chip will remain in
receive mode until a packet is successfully
received or the RX termination timer expires
(see Section 19.7). The probability that a false
sync word is detected can be reduced by
using PQT, CS, maximum sync word length,
and sync word qualifier mode as described in
Section 17. After a packet is successfully
received, the radio controller goes to the state
indicated by the MCSM1.RXOFF_MODE setting.
The possible destinations are:
3
Not forced in IDLE by issuing an SIDLE
strobe
 IDLE
 FSTXON: Frequency synthesizer on and
ready at the TX frequency. Activate TX
with STX
 TX: Start sending preamble
 RX: Start search for a new packet
Similarly, when TX is active the chip will
remain in the TX state until the current packet
has been successfully transmitted. Then the
state will change as indicated by the
MCSM1.TXOFF_MODE setting. The possible
destinations are the same as for RX.
The MCU can manually change the state from
RX to TX and vice versa by using the
command strobes. If the radio controller is
currently in transmit and the SRX strobe is
used, the current transmission will be ended
and the transition to RX will be done.
If the radio controller is in RX when the STX or
SFSTXON command strobes are used, the TX-
if-CCA function will be used. If the channel is
not clear, the chip will remain in RX. The
MCSM1.CCA_MODE setting controls the
conditions for clear channel assessment. See
Section 17.5 for details.
The SIDLE command strobe can always be
used to force the radio controller to go to the
IDLE state.
Note: When MCSM1.RXOFF_MODE=11
and a packet has been received, it will
take some time before a valid RSSI value
is present in the RSSI register again even
if the radio has never exited RX mode.
This time is the same as the RSSI
response time discussed in DN505 [12].

Texas Instruments CC1101 Specifications

General

Brand	Texas Instruments
Model	CC1101
Category	Transceiver
Language	English