decaWave DW1000, User Manual

Page: 99 / 242

DW1000 User Manual
© Decawave Ltd 2017 Version 2.12 Page 99 of 242
Register file: 0x14 – Receiver Time Tracking Offset is in the RX double-buffered swinging-set. See section
4.3 – Double Receive Buffer for more details.
The RX_TTCKO register contains the following sub-fields which are updated when a frame demodulation is
completed successfully:
REG:14:00 – RX_TTCKO – Receiver Time Tracking Offset (Octets 0 to 3, 32-bits)
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RSMPDEL - - - - - RXTOFS
0 - - - - - 0
REG:14:04 – RX_TTCKO – Receiver Time Tracking Offset (Octet 4, 8-bits)
7 6 5 4 3 2 1 0
- RCPHASE
- 0
The individual sub-fields are described below:
Field Description of fields within Register file: 0x14 – Receiver Time Tracking Offset
RXTOFS
reg:14:00
bits:18–0
RX time tracking offset. The value here is the offset measured over the interval reported in
the RXTTCKI field of
Register file: 0x13 – Receiver Time Tracking Interval . This RXTOFS value is a
19-bit signed quantity. The clock offset is calculated by dividing RXTOFS by RXTTCKI
Example (a): Say RXTOFS is reported as 0x000e4, and RXTTCKI is 0x01f00000 then this gives a
clock offset of 228 ÷ 32505856, which is 7.014E-06 or 7 ppm offset. So, the remote
transmitter’s clock is running faster than the local receiver’s clock by this 7 ppm amount.
Example (b): Say RXTOFS is reported as 0x7FF5C, and RXTTCKI is 0x01f00000 then this gives a
clock offset of -164 ÷ 32505856, which is -5.045E-06 or -5 ppm offset. So, the remote
transmitter’s clock is running slower than the local receiver’s clock by this 5 ppm amount.
- Bits marked ‘-’ are reserved and should always be written as zero.
RSMPDEL
reg:14:00
bits:31–24
This 8-bit field reports an internal re-sampler delay value. This is not expected to be of any
direct use to the host system. It was of interest in the past during the development of the IC
receiver and the leading edge determination algorithm.
RCPHASE
reg:14:04
bits:6–0
This 7-bit field reports the receive carrier phase adjustment at time the ranging timestamp is
made. This gives the phase (7 bits = 360 degrees) of the internal carrier tracking loop at the
time that the RX timestamp is received. This can be used to partially compensate for the phase
offset in the CIR’s between two DW1000 devices.
7.2.23 Register file: 0x15
– Receive Time Stamp
ID
Length
(octets)
Type Mnemonic Description
0x15 14 ROD RX_TIME Receive Time Stamp- included in swinging set
Register map register file 0x15 reports the receive time stamp and related information. During frame
reception the SFD detection event marking the end of the preamble and the start of the PHR is the nominal
point which is time-stamped by the IC. The IEEE 802.15.4 UWB standard calls this point the RMARKER.