CC2520_11 Datasheet, PDF (75/133 Pages) Texas Instruments – 2.4 GHZ IEEE 802.15.4/ZIGBEE RF TRANSCEIVER

CC2520 DATASHEET
2.4 GHZ IEEE 802.15.4/ZIGBEE® RF TRANSCEIVER
SWRS068 – DECEMBER 2007
Filtering Algorithm
The FRMFILT0.FRM_FILTER_EN bit controls whether frame filtering is applied or not. When disabled, the
CC2520 will accept all received frames. When enabled (which is the default setting), the CC2520 will only
accept frames that fulfill all of the following requirements:
• The length byte must be equal to or higher than the “minimum frame length”, which is derived from the
source- and destination address mode and PAN ID compression subfields of the FCF.
• The reserved FCF bits [9:7] and’ed together with FRMFILT0.FCF_RESERVED_BITMASK must equal
0b000.
• The value of the frame version subfield of the FCF cannot be higher than
FRMFILT0.MAX_FRAME_VERSION.
• The source and destination address modes cannot be reserved values (1).
• Destination address:
• If a destination PAN ID is included in the frame, it must match LOCAL_PANID or must be the
broadcast PAN identifier (0xFFFF).
• If a short destination address is included in the frame, it must match either LOCAL_SHORT_ADDR
or the broadcast address (0xFFFF).
• If an extended destination address is included in the frame, it must match LOCAL_EXT_ADDR.
• Frame type:
• Beacon frames (0) are only accepted when:
• FRMFILT1.ACCEPT_FT0_BEACON = 1
• Length byte >= 9
• The destination address mode is 0 (no destination address)
• The source address mode is 2 or 3 (i.e. a source address is included)
• The source PAN ID matches LOCAL_PANID, or LOCAL_PANID equals 0xFFFF
• Data (1) frames are only accepted when:
• FRMFILT1.ACCEPT_FT1_DATA = 1
• Length byte >= 9
• A destination address and/or source address is included in the frame. If no destination address
is included in the frame, the FRMFILT0.PAN_COORDINATOR bit must be set and the source
PAN ID must equal LOCAL_PANID.
• Acknowledgment (2) frames are only accepted when:
• FRMFILT1.ACCEPT_FT2_ACK = 1
• Length byte = 5
• MAC command (3) frames are only accepted when:
• FRMFILT1.ACCEPT_FT3_MAC_CMD = 1
• Length byte >= 9
• A destination address and/or source address is included in the frame. If no destination address
is included in the frame, the FRMFILT0.PAN_COORDINATOR bit must be set and the source
PAN ID must equal LOCAL_PANID for the frame to be accepted..
• Reserved frame types (4, 5, 6 and 7) are only accepted when:
• FRMFILT1.ACCEPT_FT4TO7_RESERVED = 1 (default is 0)
• Length byte >= 9
The following operations are performed before the filtering begins, with no effect on the frame data stored in
the RX FIFO:
• Bit 7 of the length byte is masked out (don’t care).
• If FRMFILT1.MODIFY_FT_FILTER is unlike zero, the MSB of the frame type subfield of the FCF is
either inverted or forced to 0 or 1.
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