Receive Mode
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–
If a destination PAN ID is included in the frame, it must match PAN_ID or must be the broadcast
PAN identifier (0xFFFF).
– If a short destination address is included in the frame, it must match either SHORT_ADDR or the
broadcast address (0xFFFF).
– If an extended destination address is included in the frame, it must match 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 PAN_ID, or PAN_ID 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 PAN_ID.
– 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 PAN_ID 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 RXFIFO:
• Bit 7 of the length byte is masked out (don't care).
• If FRMFILT1.MODIFY_FT_FILTER is not equal to zero, the MSB of the frame type subfield of the FCF
is either inverted or forced to 0 or 1.
If a frame is rejected, the radio only starts searching for a new frame after the rejected frame has been
completely received (as defined by the frame-length field) to avoid detecting false SFDs within the frame.
Note that a rejected frame can generate RX overflow if it occurs before the frame is rejected.
Interrupts
When frame filtering is enabled and the filtering algorithm accepts a received frame, an
RX_FRM_ACCEPTED interrupt is generated. It is not generated if frame filtering is disabled or
RX_OVERFLOW or RX_FRM_ABORTED is generated before the filtering result is known.
Figure 23-12 illustrates the three different scenarios (not including the overflow and abort-error conditions).
236
CC253x Radio SWRU191C–April 2009–Revised January 2012
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