
DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 76 of 242
Field
Description of fields within Register file: 0x08 – Transmit Frame Control
TXPSR
reg:08:00
bits:19,18
Transmit Preamble Symbol Repetitions (PSR). This sets the length of the transmitted preamble
sequence in symbols. Each preamble symbol is approximately 1 µs in duration
1
.The two TXPSR
bits are copied into the PHY Header. The receiving end is thus made aware of how much
preamble was sent. This might inform its choice of preamble length in any reply message.
There are four standard preamble lengths are defined for the 802.15.4 UWB PHY – these are
16, 64, 1024 and 4096 symbols. The DW1000 has facility via the PE (Preamble Extension)
configuration to send preambles of additional (non-standard) intermediary lengths. Table 16
below lists the selectable preamble lengths.
PE
reg:08:00
bits:21,20
Preamble Extension. This field allows specification of a non-standard number of preamble
symbol repetitions, thus extending the set of preamble lengths that are available to optimise
system performance. The resultant preamble lengths depend the setting of both PE and
TXPSR above. Table 16 below lists the useful preamble lengths that can be selected.
Table 16: Preamble length selection
Bit 19
Bit 18
Bit 21
Bit 20
TXPSR
PE
Preamble Length
0
1
0
0
64
0
1
0
1
128
0
1
1
0
256
0
1
1
1
512
1
0
0
0
1024
1
0
0
1
1536
1
0
1
0
2048
1
1
0
0
4096
The bit numbers quoted above are the bit numbers in the TX_FCTRL register.
The choice of preamble length has a bearing on operating range and system performance, a
discussion of the factors affecting the choice of preamble length (and other parameters) may
be found in section 9.3 below.
TXBOFFS
reg:08:00
bits:31–22
Transmit buffer index offset. This 10-bit field is used to specify an index in the transmit buffer
of the first octet to be transmitted. The TX frame begins with the octet at the TXBOFFS index
and continues for the number octets specified by the frame length (TFLEN and TFLE) less 2 for
the CRC. Care should be taken that the TXBOFFS plus the frame length does not extend past
the end of the TX_BUFFER. Some uses for TXBOFFS are outlined in section 3.5.1
1
The duration of preamble symbols is 993.59 ns with the 16 MHz PRF setting and 1017.63 ns with for 64 MHz PRF.