DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 81 of 242
Field
Description of fields within Register file: 0x0D – System Control Register
TXDLYS
reg:0D:00
bit:2
Transmitter Delayed Sending. This control works in conjunction with TXSTRT and the DX_TIME
value specified by
Register file: 0x0A – Delayed Send or Receive Time
. When the user wants to
control the time of sending of a frame, the send time is programmed into DX_TIME, and then
both TXDLYS and TXSTRT should be set at the same time to correctly invoke the delayed
sending feature. The TXDLYS bit will clear along with the TXSTRT bit when the delay has
completed and the frame transmission begins and initiates the delayed transmission.
When delayed sending is used the DW1000 precisely controls the transmission start time so
that the internal TX timestamp occurs at the point when SYS_TIME is equal to the DX_TIME
value. The actual time of TX then is calculable as DX_TIME plus the TX antenna delay.
TXDLYS has a number of uses: -
It can be used to give precise control of the transmission time of a response message,
which would allow a receiver that knows this response time to only turn on at the
correct time to receive the response, thus saving power.
In symmetric double-sided two-way ranging, the RX to TX response times at either end
should be the same so that their differences in local clocks correctly cancel out. This
may be ensured by setting TXDLYS to a value that is a fixed delta added to the RX time-
stamp.
In two-way ranging the TX timestamp of the final message exchange needs to be
communicated to the receiving end to allow the round-trip delay to be calculated.
Using TXDLYS allows this time to be predicted, pre-calculated and embedded into the
final message itself. This may save the need for an additional message interchange
which will give a power saving, and save time too.
Embedding the TX time in this way may also reduce the number of messages in a
wireless clock synchronisation scheme.
CANSFCS
reg:0D:00
bit:3
Cancel Suppression of auto-FCS transmission (on the current frame). This bit is intended to be
used when transmission is kicked off before the data is actually written to the transmit buffer,
which can be used to speed response times and/or system data throughput. A general
discussion of these techniques may be found in section
The general principle is not to send the FCS (marking a good frame) until all the data is written
to the TX_BUFFER. So transmission is initiated with SFCST set to suppress the FCS and when
all data is written to the TX_BUFFER the FCS transmission is enabled by setting the CANSFCS
bit to cancel the suppression, i.e. allow the transmission of the FCS. The DW1000 transmitter
includes a circuit to detect the host microprocessor writing to the buffer between the
configured TXBOFFS and any address it has already consumed data from, which is taken to
mean the HOST has written the data too late for transmission, in which case the setting of
CANSFCS will be ignored and the frame will be transmitted with a bad CRC. This condition is
signalled by the TXBERR bit in
Register file: 0x0F – System Event Status Register
bit will clear as soon as the DW1000 sees and acts on it.
TRXOFF
reg:0D:00
bit:6
Transceiver Off. When this is set the DW1000 returns to idle mode immediately. Any TX or RX
activity that is in progress at that time will be aborted. The TRXOFF bit will clear as soon as the
DW1000 sees it and returns the IC to idle mode.