DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 29 of 242
number of preamble symbols received to additionally inform the choice of preamble length for any response
frames.
The SECDED (single error correct, double error detect) field, S5–S0, is a set of six parity check bits that are
used to protect the PHR from errors caused by noise and channel impairments. The SECDED calculation is
the same as that defined in the IEEE 802.15.4-2011 standard except the bits C5–C0 are inverted to get S5–S0
as follows:
S0 =
NOT
(C0)
S1 =
NOT
(C1)
S2 =
NOT (
C2)
S3 =
NOT
(C3)
S4 =
NOT
(C4)
S5 =
NOT
(C5)
3.5 High Speed Transmission
Certain features of the DW1000 are designed to support maximum utilisation of the transmitter. These
features are described below:
3.5.1 TX buffer offset index
The TXBOFFS field (in
Register file: 0x08 – Transmit Frame Control
) allows the TX_BUFFER to be used to hold
more than one frame, (providing that data can fit within the 1024 octets of the buffer). In initiating a
transmission then the host controller will set the TXBOFFS offset index to the first octet of the frame to be
transmitted and set the length field to reflect the length of the frame to send. While sending is in progress,
the host controller can prepare and write another frame to a different part of the TX_BUFFER. After
transmission of the first frame then, the host has saved the time needed to write the next data frame, and
just needs to set the offset and initiate the transmission of the next frame.
During a data streaming or bulk data transfer then the host controller might divide the TX_BUFFER into two
areas of 512 octets each, sending from them alternately. For acknowledged data transfer then: the receipt
of the acknowledgement for frame, frame “A” (say), can be used to trigger the sending of the next frame,
frame “B” (say), that is already waiting in the other half of the buffer and at the same time signalling that the
buffer half that contained the acknowledged frame “A” can now, (while frame “B” is being transmitted), be
filled with the data for the subsequent frame, frame “C” (say). Where the acknowledgement for frame “A” is
not received, the data for it is still in the TX_BUFFER ready to be retransmitted.
3.5.2 TX buffer write while sending or receiving
For fast turnaround it is possible to initiate preamble sending before writing the frame data to the
TX_BUFFER or writing the frame length to the length as specified in the TFLEN and TFLE fields of the
file: 0x08 – Transmit Frame Control
. So preamble transmission can begin before the TX data is written into
the DW1000. The host microprocessor then has the time of any fixed response delay, and the time for
sending preamble and SFD before it needs to have the frame length set in TFLEN and TFLE ready for the