CC112X/CC1175
SWRU295C
Page 42 of 108
7
Packet Handling Hardware Support
The
CC112X
has built-in hardware support for packet oriented radio protocols.
In transmit mode, the packet handler can be configured to add the following elements to the packet
stored in the TX FIFO:
A programmable number of preamble bytes
An 11, 16, 18, 24 or 32 bit synchronization word
A 2 byte CRC checksum computed over the data field.
Whitening of the data with a PN9 sequence
In receive mode, the packet handling support will de-construct the data packet by implementing the
following (if enabled):
Preamble detection
Sync word detection
CRC computation and CRC check
One byte address check
Packet length check (length byte checked against a programmable maximum length)
De-whitening
Optionally, two status bytes (see Table 22 and Table 23) with RSSI value, Link Quality Indication, and
CRC status can be appended in the RX FIFO by setting
.
Bit Field Name
Description
7:0
RSSI
RSSI value
Table 22: Received Packet Status Byte 1
(first byte appended after the data)
Bit Field Name
Description
7
CRC_OK
1: CRC for received data OK
(or CRC disabled or TX mode)
0: CRC error in received data
6:0
LQI
Indicating the link quality
Table 23: Received Packet Status Byte 2
(second byte appended after the data)
7.1
Standard Packet Format
The format of the data packet can be configured and consists of the following items (see Figure 16):
Preamble
Synchronization word
Optional length byte
Optional address byte
Payload
Optional 2 byte CRC
Preamble bits
S
y
n
c
w
o
rd
L
e
n
g
th
f
ie
ld
A
d
d
re
s
s
f
ie
ld
Data field
C
R
C
-1
6
Optional CRC-16 calculation
8 x
n
bits
max 32
bits
8
bits
8
bits
8 x n bits
16 bits
Optional data whitening
Legend:
Inserted automatically in TX,
processed and removed in RX.
Optional user-provided fields processed in TX,
processed but not removed in RX.
Unprocessed user data (apart from
whitening)
Figure 16: Packet Format