5.2.2 Frame Filtering Notes
The frame filtering does not take any notice of the Security Enabled field, in the frame control, so it is up to
the host software to decode any security information and accept/reject the frame is it sees fit. See section
11.2.2 – Security enabled Field for details.
The decisions on frame rejection/acceptance with respect to illegal frame control octets is made after the
first two octets of data are decoded, and at the end of reception of the address fields (as specified by the
frame control octets) for the relevant addressing rules. When a frame is rejected, the reception is aborted
immediately and the rejection is reported by the AFFREJ event bit in Register file: 0x0F – System Event Status
Register.
While frame filtering can save some work on the part of the host system, prolonged listening with the
DW1000 receiver on is a relatively power hungry activity best employed only on equipment with a mains
powered source.
All the configuration bits related to frame filtering are in Register file: 0x04 – System Configuration.
5.3 Automatic Acknowledgement
The automatic acknowledgement functionality of the DW1000 allows the IC to automatically send
acknowledgement frames when a frame is received and validated that includes an acknowledgement
request. The automatic acknowledgement functionality only operates when frame filtering is enabled and
automatic acknowledgement is enabled.
In order for automatic acknowledgement to operate:
• Frame filtering must be enabled and the received data or MAC command frame must be
correctly addressed and pass through the receive frame filtering, (see section 5.2 - Frame
filteringfor details of frame filtering configuration).
• The ACK request bit in the frame control field of the received frame must be set.
• Auto-acknowledgement must be enabled by the AUTOACK configuration in Register file: 0x04 –
System Configuration.
When these conditions are met the DW1000 will at the end of the reception automatically transition into
transmit mode to send the 5-octet MAC acknowledgement frame as defined by IEEE 802.15.4-2011.
If automatic acknowledgement and double buffering are intended to be used together, the system must be
designed such that overruns cannot occur, or if they can occur, that the system can deal with
acknowledgement of frames which subsequently become corrupted, see section 4.3.5.
5.3.1 Preamble length & SFD in Automatic Acknowledge Frame
5.3.1.1 Preamble length
The preamble length of the frame requesting acknowledgement (ACK) is encoded in the PHR of that frame,
(see section 10.4 – PHY header), and decoded in the DW1000 receiver (and reported in the RXPSR field of
Register file: 0x10 – RX Frame Information Register). This only covers preamble lengths defined in the IEEE
802.14.4 standard, but the DW1000 supports other preamble lengths. To cope with this the DW1000 selects
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