Texas Instruments CC112 Series, User Manual, Page: 61 / 109

CC112X/CC1175
SWRU295C Page 61 of 108
TX
Time
Time
TX TX
1.x s 1.x s
1 s 1 s
1.x s
TX
1 s
RX RX RX
Pr sync
Payload
XOSC Start-Up
RX Timeout
Extra time in RX
to receive the packet
Figure 27: eWOR Mode (RX and TX out of sync.)
In this case, the
WOR_CAPTURE1
and
WOR_CAPTURE0
registers on the receivers would show a higher
and higher value for every packet received, indicating that the transmitter is sending at a slower rate
than t
EVENT0
. The receiver should therefore increase t
EVENT0
to stay in sync with the transmitter (see
Figure 28).
TX
Time
TX TX
1.x s 1.x s
1 s
TX
1.x s
1.x s 1.x s
RX RX RX RX
Pr sync
Payload
XOSC Start-Up
RX Timeout
Extra time in RX
to receive the packet
Figure 28: eWOR Mode (RX and TX re-synchronized)
8.7 RX Sniff Mode
For battery operated systems the RX current is an important parameter and to increase battery
lifetime a novel RX Sniff Mode feature has been designed for the
CC112X
family to autonomously sniff
for RF activity using an ultra low power algorithm. RX Sniff Mode is enabled by using eWOR together
with RX termination based on CS (see 8.5.2) or PQT (see 8.5.3).
The
CC112X
platform is designed for extremely fast settling time hence the receiver can be turned on
and off quickly. Together with the ability to quickly and reliably detect if there is RF activity or not this
is a key parameter to reduce the power consumption.
The
CC112X
family use strong DSP logic to detect a sync word and the preamble is only needed for
AGC settling, i.e. settling the gain of the front end. A 4 bits preamble is enough for settling including
frequency offset compensation (AFC).