CC112X/CC1175
SWRU295C
Page 53 of 108
8
Radio Control
CC112X
has a built-in state machine that is used to switch between different operational states
(modes). The change of state is done either by using command strobes or by internal events such as
TX FIFO underflow.
A simplified state diagram is shown in Figure 2. The numbers refer to the state numbers readable
from the
8.1
Power-On Start-Up Sequence
When the power supply is turned on, the system must be reset. This is achieved by one of the two
sequences described below, i.e. automatic power-on reset (POR) or manual reset.
8.1.1
Automatic POR
A power-on reset circuit is included in the
CC112X
. The internal power-up sequence is completed when
goes low.
is observed on the SO pin after CSn is pulled low (See Section
3.1.2 for more details).
When the
CC112X
reset is completed, the chip will be in the IDLE state and the crystal oscillator will be
running. If the chip has had sufficient time for the crystal oscillator to stabilize after the power-on-
reset, the SO pin will go low immediately after taking CSn low. If CSn is taken low before reset is
completed, the SO pin will first go high, indicating that the crystal oscillator is not stabilized, before
going low as shown in Figure 21.
XOSC Stable
CSn
SO
Figure 21: Power-On Reset
8.1.2
Manual Reset
The other reset possibilities on the
CC112X
command strobe or using the
RESET_N pin. By issuing a manual reset, all internal registers are set to their default values and the
radio will enter IDLE state.
8.2
Crystal Control
The
crystal
oscillator
(XOSC)
is
either
automatically
controlled
or
always
on,
if
XOSC2.XOSC_CORE_PD_OVERRIDE = 1
. If the XOSC is forced on, the crystal will always stay on
, or
command strobe has been issued. This can be used to enable fast
start-up
from
SLEEP/XOFF
at
the
expense
of
a
higher
current
consumption.
If
XOSC2.XOSC_CORE_PD_OVERRIDE = 0
, the XOSC will be turned off if the
command strobes are issued; the state machine then goes to XOFF or SLEEP state. This can only be
done from the IDLE state. The XOSC will be automatically turned on again when CSn goes low, and
the radio will enter IDLE state. The SO pin on the SPI interface must be pulled low before the SPI
interface is ready to be used, as described in Section 3.1.2.
Crystal oscillator start-up time depends on crystal ESR and load capacitances.
8.3
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
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.