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CC112X/CC1175
SWRU295C
Page 48 of 108
7.2
Packet Filtering in Receive Mode
CC112X
supports three different types of packet-filtering; address filtering, maximum length filtering, and
CRC filtering.
7.2.1
Address Filtering
Setting
to any other value than zero enables the address filtering
where the packet handler engine will compare the address field in the packet (see Figure 16) with the
programmed node address in the
PKT_CFG1.ADDR_CHECK_CFG = 10b
it will
in addition check against the 0x00 broadcast address, or both the 0x00 and 0xFF broadcast
addresses when
PKT_CFG1.ADDR_CHECK_CFG = 11b
. If the received address matches a valid
address, the packet is received and written into the RX FIFO. If the address match fails, the packet is
discarded and the radio controller will either restart RX or go to IDLE dependent on the
RFEND_CFG0.TERM_ON_BAD_PACKET_EN
ignored
14
).
7.2.2
Maximum Length Filtering
In variable packet length mode,
used to set the maximum allowed packet length. If the received length byte has a larger value than
this, the packet is discarded and the radio controller will either restart RX or go to IDLE dependent on
the
RFEND_CFG0.TERM_ON_BAD_PACKET_EN
setting is
ignored).
7.2.3
CRC Filtering
The
filtering
of
a
packet
when
CRC
check
fails
is
enabled
by
setting
. The CRC auto flush function will only flush the packet received
with bad CRC, other packets will remain unchanged in the RX FIFO. After auto flushing the faulty
packet, the radio controller will either restart RX or go to IDLE dependent on the
RFEND_CFG0.TERM_ON_BAD_PACKET_EN
setting is
ignored).
When using the auto flush function, the maximum packet length is 127 bytes in variable packet length
mode and 128 bytes in fixed packet length mode. Note that when
enabled, the maximum allowed packet length is reduced by two bytes in order to make room in the
RX FIFO for the two status bytes appended at the end of the packet. The MCU must not read from
the current packet until the CRC has been checked as OK.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
.
.
.
124
125
126
127
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
.
.
.
124
125
126
127
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
.
.
.
124
125
126
127
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
.
.
.
124
125
126
127
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
.
.
.
124
125
126
127
RXLAST
RXLAST
RXLAST
RXLAST
RXLAST
CRC Error
1st packet
CRC OK
2nd packet
CRC OK
3rd packet
CRC Error
4th packet
CRC OK
RXLAST
RX FIFO is
empty
Figure 20: CRC Autoflush of Faulty Packet
14
can be changed while in active mode