CC1110Fx / CC1111Fx
the preamble quality must be exceeded in
order for a detected sync word to be accepted.
See Section 14.10.2 on page 196 for more
details.
configured through the SYNC1 and SYNC0
registers and is sent MSB first.
In order to make false detections of sync
words less likely,
a
mechanism called
preamble quality indication (PQI) can be used
to qualify the sync word. A threshold value for
14.8 Packet Handling Hardware Support
The CC1110Fx/CC1111Fx has built-in hardware
support for packet oriented radio protocols.
Bit
Field Name
Description
7:0
RSSI
RSSI value
In transmit mode, the packet handler can be
configured to add the following elements to the
packet:
Table 65: Received Packet Status Byte 1
(first byte appended after the data)
Bit
Field name
Description
• A programmable number of preamble
bytes
7
CRC_OK
1: CRC for received data OK (or
CRC disabled)
• A two byte synchronization (sync) word.
Can be duplicated to give a 4-byte sync
word (recommended). It is not possible
to only insert preamble or only insert a
sync word.
0: CRC error in received data
6:0
LQI
The
Link
Quality
Indicator
estimates how easily a received
signal can be demodulated
• A CRC checksum computed over the
data field
Table 66: Received Packet Status Byte 2
(second byte appended after the data)
The recommended setting is 4-byte preamble
and 4-byte sync word, except for 500 kBaud
data rate where the recommended preamble
length is 8 bytes.
Note that register fields that control the packet
handling features should only be altered when
CC1110Fx/CC1111Fx is in the IDLE state.
In addition, the following can be implemented
on the data field and the optional 2-byte CRC
checksum:
14.8.1 Data Whitening
From a radio perspective, the ideal over the air
data are random and DC free. This results in
the smoothest power distribution over the
occupied bandwidth. This also gives the
regulation loops in the receiver uniform
operation conditions (no data dependencies).
• Whitening of the data with a PN9
sequence.
• Forward error correction by the use of
interleaving and coding of the data
(convolutional coding).
In receive mode, the packet handling support
will de-construct the data packet by
implementing the following (if enabled):
Real world data often contain long sequences
of zeros and ones. Performance can then be
improved by whitening the data before
transmitting, and de-whitening the data in the
receiver. With CC1110Fx/CC1111Fx, this can be
• Preamble detection
• Sync word detection
• CRC computation and CRC check
• One byte address check
• Packet length check (length byte
done
automatically
by
setting
PKTCTRL0.WHITE_DATA=1. All data, except
the preamble and the sync word, are then
XOR-ed with a 9-bit pseudo-random (PN9)
sequence before being transmitted as shown
in Figure 49. At the receiver end, the data are
XOR-ed with the same pseudo-random
sequence. This way, the whitening is reversed,
and the original data appear in the receiver.
The PN9 sequence is reset to all 1’s.
checked against
maximum length)
• De-whitening
a
programmable
• De-interleaving and decoding
Optionally, two status bytes (see Table 65 and
Table 66) with RSSI value, Link Quality
Indication, and CRC status can be appended
to the received packet.
Data whitening can only be used when
PKTCTRL0.CC2400_EN=0(default).
SWRS033E
Page 192 of 239
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