C2510Fx / CC2511Fx
The MSK modulation format implemented in
data compared to e.g. signal generators.
CC2510Fx/CC2511Fx inverts the sync word and
14.10 Received Signal Qualifiers and Link Quality Information
register and perform the packet filtering
CC2510Fx/CC2511Fx has several qualifiers that
can be used to increase the likelihood that a
valid sync word is detected.
described in Section 14.8.3 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 14.10.4.
14.10.1
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
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
No preamble/sync, carrier sense
above threshold
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
14.10.2
Preamble Quality Threshold (PQT)
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.
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.
14.10.3
RSSI
Another use of the preamble quality threshold
is as a qualifier for the optional RX termination
timer. See Section 14.12.3 on Page 206 for
details.
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.
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·PQTfor
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.
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. The
RSSI value is in dBm with ½ dB resolution.
The RSSI update rate, fRSSI, depends on the
receiver filter bandwidth (BWchannel defined in
Section
14.6)
and
A “Preamble Quality Reached” signal can be
observed on P1_5, P1_6, or P1_7 by setting
AGCCTRL0.FILTER_LENGTH.
SWRS055D
Page 198 of 243
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