Texas Instruments CC112 Series, User Manual, Page: 58 / 109

CC112X/CC1175
SWRU295C Page 58 of 108
8.6 Enhanced Wake on Radio (eWOR)
The optional enhanced Wake on Radio (eWOR) functionality enables
CC112X
to periodically wake up
from SLEEP and listen for incoming packets without MCU interaction.
When the
SWOR
strobe command is sent on the SPI interface, the
CC112X
will go to the SLEEP state
when CSn is released. Unless an external 32 kHz crystal is used (
EXT_CTRL.EXT_32K_CLOCK_EN
= 1
) the RC oscillator must be enabled by setting
WOR_CFG0.RC_PD = 0
before the
SWOR
strobe is
issued, as it is the clock source for the eWOR timer (see Section 8.8 for more info on the RC
oscillator). The on-chip eWOR timer will set
CC112X
into IDLE state and then RX state. After a
programmable time in RX (see Section 8.5.1), the chip will go back to the SLEEP state, unless a
packet is received.
To exit eWOR mode, CSn must be pulled low.
The on-chip eWOR timer will be clocked, independently of eWOR mode, whenever the RC oscillator
is running. This preserves the timing when exiting eWOR mode. The on-chip eWOR timer can be
reset to the Event 1 value by issuing the
SWORRST
strobe command. The value of the eWOR timer is
available through
WOR_TIME1
and
WOR_TIME0
.
Every time a sync word is found, the current value of the eWOR timer will be captured and it can be
read through the
WOR_CAPTURE1
and
WOR_CAPTURE0
registers. This feature is useful in applications
where re-synchronization of the eWOR timer is required.
CC112X
can be set up to signal the MCU that a packet has been received by using a GPIO pin. When
the MCU has read the packet, it can put the chip back into SLEEP with the
SWOR
strobe from the IDLE
state.
8.6.1 WOR EVENT 0, 1, and 2
The eWOR timer has three events, Event 0, Event 1, and Event 2. In the SLEEP state with eWOR
activated, reaching Event 0 will turn on the digital regulator and start the crystal oscillator (unless
WOR_CFG1.WOR_MODE = 100b
). Event 1 follows Event 0 after a programmed timeout (t
Event1
).
Figure 25 shows the timing relationship between Event 0 timeout and Event 1 timeout.
t
Event0
t
Event1
Event1 Event0 Event1 Event0
t
Event1
t
Event0
t
State: IDLE SLEEP RX SLEEP IDLE
RX
Rx Timeout
t
SLEEP
Figure 25: Event 0 and Event 1 Relationship
The time between two consecutive Event 0‟s is programmed with a mantissa value given by
WOR_EVENT0_MSB
and
WOR_EVENT0_LSB
and an exponent value set by
WOR_CFG1.WOR_RES
. t
Event0
is given by Equation 20.
RES WOR
RCOSC
Event
EVENT
f
t
_ 5
0
2 0
1
Equation 20: t
Event0
The Event 1 timeout is programmed with a mantissa value decoded by the
WOR_CFG1.EVENT1
setting.