CC1110Fx / CC1111Fx
byte (optionally 4-byte) sync word and then the
content of the RFD register. If CRC is enabled,
the checksum is calculated over all the data
pulled from the RFD register and the result is
sent as two extra bytes following the payload
data. If fewer bytes are written to the RFD
registers than what the radio expects the radio
will enter TX_UNDERFLOW state and the
RFIF.IRQ_TXUNF flag will be set together
with RFIF.IRQ_DONE. An SIDLE strobe needs
to be issued to return to IDLE state.
the optional CRC. The PKTLEN register is
used to set the maximum packet length
allowed in RX. Any packet received with a
length byte with a value greater than PKTLEN
will be discarded.
14.8.3 Packet Filtering in Receive Mode
CC2500 supports two different types of packet-
filtering: address filtering and maximum length
filtering.
14.8.3.1Address Filtering
If whitening is enabled, everything following
the sync words will be whitened. This is done
before the optional FEC/Interleaver stage.
Setting PKTCTRL1.ADR_CHK to any other
value than zero enables the packet address
filter. The packet handler engine will compare
the destination address byte in the packet with
the programmed node address in the ADDR
register and the 0x00 broadcast address when
PKTCTRL1.ADR_CHK=10 or both 0x00 and
Whitening
is
enabled
by
setting
PKTCTRL0.WHITE_DATA=1.
If FEC/Interleaving is enabled, everything
following the sync words will be scrambled by
the interleaver and FEC encoded before being
modulated. FEC is enabled by setting
MDMCFG1.FEC_EN=1.
0xFF
broadcast
addresses
when
PKTCTRL1.ADR_CHK=11. If the received
address matches a valid address, the packet is
accepted and the RFTXRXIF flag is asserted
and a DMA trigger is generated. If the address
match fails, the packet is discarded and
receive mode restarted (regardless of the
MCSM1.RXOFF_MODE
RFIF.IRQ_DONE flag will be asserted but the
DMA will not be triggered.
14.8.5 Packet Handling in Receive Mode
In receive mode, the demodulator and packet
handler will search for a valid preamble and
the sync word. When found, the demodulator
has obtained both bit and byte synchronism
and will receive the first payload byte.
setting).
The
If FEC/Interleaving is enabled, the FEC
decoder will start to decode the first payload
byte. The interleaver will de-scramble the bits
before any other processing is done to the
data.
14.8.3.2 Maximum Length Filtering
In
variable
packet
length
mode,
the
PKTCTRL0.LENGTH_CONFIG=1,
PKTLEN.PACKET_LENGTH register value is
used to set the maximum allowed packet
length. If the received length byte has a larger
value than this, the packet is discarded and
receive mode restarted (regardless of the
If whitening is enabled, the data will be de-
whitened at this stage.
When variable packet length mode is enabled,
the first byte is the length byte. The packet
handler stores this value as the packet length
and receives the number of bytes indicated by
the length byte. If fixed packet length mode is
used, the packet handler will accept the
programmed number of bytes.
MCSM1.RXOFF_MODE
setting).
The
RFIF.IRQ_DONE flag will be asserted but the
DMA will not be triggered.
14.8.4 Packet Handling in Transmit Mode
Next, the packet handler optionally checks the
address and only continues the reception if the
address matches. If automatic CRC check is
enabled, the packet handler computes CRC
and matches it with the appended CRC
checksum.
The payload that is to be transmitted must be
written into RFD. The first byte written must be
the length byte when variable packet length is
enabled. The length byte has a value equal to
the payload of the packet (including the
optional address byte). If fixed packet length is
enabled, then the first byte written to RFD is
interpreted as the destination address, if this
feature is enabled in the device that receives
the packet.
At the end of the payload, the packet handler
will optionally write two extra packet status
bytes that contain CRC status, link quality
indication and RSSI value.
The modulator will first send the programmed
number of preamble bytes. If data has been
written to RFD, the modulator will send the two-
If a byte is received in the RFDregister, and it
is not read before the next byte is received, the
SWRS033E
Page 194 of 239
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