decaWave DW1000 - Page 80

DW1000 User Manual
© Decawave Ltd 2017
Version 2.12
Page 80 of 242
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HRBPT
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RXDLYE
RXENAB
WAIT4RESP
TRXOFF
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CANSFCS
TXDLYS
TXSTRT
SFCST
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Field
Description of fields within Register file: 0x0D – System Control Register
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Bits marked ‘-’ in register 0x0D are reserved and should always be written as zero.
SFCST
reg:0D:00
bit:0
Suppress auto-FCS Transmission (on this next frame). This control works in conjunction with
the TXSTRT (Transmit Start) bit below to control whether or not the DW1000 automatically
calculates and appends the two Frame-Check-Sequence bytes. It is expected that the host will
decide this as transmission is invoked and set SFCST at the same time as TXSTRT is set if FCS
suppression is required. Normally SFCST is not set when transmission is started and the
DW1000 calculates the FCS on the octets fetched from the TX buffer, and automatically
appends the two-byte FCS sequence at the end of the frame. The FCS sequence follows the
IEEE 802.15.4 standard polynomial, x
16
+ x
12
+ x
5
+ 1, also known as CRC-16-CCITT or CRC-16
ITU-T. When SFCST is set (as transmission is started) the DW1000 will not append the FCS to
the data frame but instead fetches the two bytes from the TX buffer. The frame length is
determined by the TFLEN field of Register file: 0x08 – Transmit Frame Control. So, when SFCST
is clear, TFLEN-2 (frame length minus two) octets are fetched and sent from the TX buffer, and
the final two octets sent are the automatically generated FCS bytes. And, when SFCST is set,
TFLEN (frame length) octets are sent from the TX buffer. SFCST may be of use if a non-
standard IEEE 802.15.4 frame protocol is being employed, and can also be of use to induce a
FCS error in the remote receiver during testing. The SFCST bit will clear as soon as the DW1000
sees TXSTRT and initiates transmission.
TXSTRT
reg:0D:00
bit:1
Transmit Start. This bit commands the DW1000 to begin transmission. When the DW1000 is
in idle mode and the TXSTRT bit is set it the IC will begin transmission of a frame immediately,
unless TXDLYS is set (see below). In general it would be expected that the user has a prepared
frame in the transmit buffer and has configured the desired transmit mode and set the frame
length, in Register file: 0x08 – Transmit Frame Control, before setting TXSTRT to invoke
transmission. For a general discussion of transmission see section 3 –Message Transmission.
The TXSTRT bit will clear when the frame transmission begins.