CC2510Fx / CC2511Fx
13.9.2 Minimum Shift Keying
equivalent to changing the shaping of the
symbol.
When using MSK21 the complete transmission
(preamble, sync word, and payload) will be
MSK modulated.
The MSK modulation format implemented in
CC2510Fx/CC2511Fx inverts the sync word and
data compared to e.g. signal generators.
Phase shifts are performed with a constant
transition time.
Note: The DEVIATN register setting
The fraction of a symbol period used to change
the phase can be modified with the
DEVIATN.DEVIATION_M setting. This is
has no effect in RX when using MSK. Also,
when
using
MSK
Manchester
encoding/decoding should be disabled
(MDMCFG2.MANCHESTER_EN=0)
21
Identical to offset QPSK with half-sine
shaping (data coding may differ)
13.10 Received Signal Qualifiers and Link Quality Information
CC2510Fx/CC2511Fx has several qualifiers
that can be used to increase the likelihood that
a valid sync word is detected.
Another use of the preamble quality threshold
is as a qualifier for the optional RX termination
timer. See Section 13.12.3 on Page 201 for
details.
The preamble quality estimator increases an
internal counter by one each time a bit is
received that is different from the previous bit,
and decreases the counter by 8 each time a bit
is received that is the same as the last bit. The
threshold is configured with the register field
PKTCTRL1.PQT. A threshold of 4·PQT for this
counter is used to gate sync word detection.
By setting the value to zero, the preamble
quality qualifier of the sync word is disabled.
13.10.1 Sync Word Qualifier
If sync word detection in RX is enabled in
register MDMCFG2 the CC2510Fx/CC2511Fx will
not start writing received data to the RFD
register and perform the packet filtering
described in Section 13.8.3 before a valid sync
word has been detected. The sync word
qualifier mode is set by MDMCFG2.SYNC_MODE
and is summarized in Table 67. Carrier sense
in Table 67 is described in Section 13.10.4.
A “Preamble Quality Reached” signal can be
observed on P1_5, P1_6, or P1_7 by setting
IOCFGx.GDOx_CFG=1000. It is also possible
to determine if preamble quality is reached by
checking the PQT_REACHED bit in the
PKTSTATUS register. This signal / bit asserts
when the received signal exceeds the PQT.
MDMCFG2.
Sync Word Qualifier Mode
SYNC_MODE
000
001
010
011
100
No preamble/sync
15/16 sync word bits detected
16/16 sync word bits detected
30/32 sync word bits detected
13.10.3 RSSI
No preamble/sync, carrier sense
above threshold
The RSSI value is an estimate of the signal
level in the chosen channel. This value is
based on the current gain setting in the RX
chain and the measured signal level in the
channel.
101
110
111
15/16 + carrier sense above threshold
16/16 + carrier sense above threshold
30/32 + carrier sense above threshold
Table 67: Sync Word Qualifier mode
In RX mode, the RSSI value can be read
continuously from the RSSI status register until
the demodulator detects a sync word (when
sync word detection is enabled). At that point
the RSSI readout value is frozen until the next
time the chip enters the RX state.
13.10.2 Preamble Quality Threshold (PQT)
The Preamble Quality Threshold (PQT) sync-
word qualifier adds the requirement that the
received sync word must be preceded with a
preamble with a quality above a programmed
threshold.
SWRS055F
Page 194 of 241
TI [ TEXAS INSTRUMENTS ]
