CC2520_11 Datasheet, PDF (123/133 Pages) Texas Instruments – 2.4 GHZ IEEE 802.15.4/ZIGBEE RF TRANSCEIVER

CC2520 DATASHEET
2.4 GHZ IEEE 802.15.4/ZIGBEE® RF TRANSCEIVER
SWRS068 – DECEMBER 2007
MDMCTRL0, A 0x046, R 0x45, Controls modem
Bit
Bit mnemonic
no.
7:6
DEM_NUM_ZEROS[1:0]
5
DEMOD_AVG_MODE
4:1
PREAMBLE_LENGTH
[3:0]
0
TX_FILTER
Reset
value
01
0
0010
1
Mode
R/W
R/W
R/W
R/W
Description
Sets how many zero symbols have to be detected before the sync
word when searching for sync. Note that only one is required to
have a correlation value above the correlation threshold set in
MDMCTRL1 register.
00 : reserved
01 : 1 zero symbols
10 : 2 zero symbols
11 : 3 zero symbols
NOTE
This value should be updated to “10” before attempting RX.
Testing has shown that the reset value causes too many false
frames to be received.
Defines the behavior or the frequency offset averaging filter.
0 - Lock average level after preamble match. Restart frequency
offset calibration when searching for the next frame.
1 - Continuously update average level.
The number of preamble bytes (2 zero-symbols) to be sent in TX
mode prior to the SFD, encoded in steps of 2. The reset value of
2 is compliant with IEEE 802.15.4
0000 - 2 leading zero bytes
0001 - 3 leading zero bytes
0010 - 4 leading zero bytes
…
1111 - 17 leading zero bytes
Defines what kind of TX filter that is used. The normal TX filter is
as defined by the IEEE802.15.4 standard. Extra filtering may be
applied in order to lower the out of band emissions.
0 - Normal TX filtering
1 - Enable extra filtering
MDMCTRL1, A 0x047, R 0x2E, Controls modem
Bit
Bit mnemonic
no.
7:6
RESERVED
5
CORR_THR_SFD
4:0
CORR_THR[4:0]
Reset
value
00
1
0x0E
Mode
R0
R/W
R/W
Description
Read as zero
Defines requirements for SFD detection:
0 - The correlation value of one of the zero symbols of the
preamble must be above the correlation threshold.
1 - The correlation value of one zero symbol of the preamble and
both symbols in the SFD must be above the correlation threshold.
NOTE
This value should be changed to ‘0’ before attempting RX. This
will give the best trade off between good sensitivity and few false
SFD detections.
Demodulator correlator threshold value, required before SFD
search.
Threshold value adjusts how the receiver synchronizes to data
from the radio. If threshold is set too low sync can more easily be
found on noise. If set too high the sensitivity will be reduced but
sync will not likely be found on noise.
I combination with DEM_NUM_ZEROS the system can be tuned
so sensitivity is high with less synch found on noise.
NOTE
This value should be changed to 0x14 before attempting RX.
Testing has shown that too many false frames are received if the
reset value is used.
WWW.TI.COM
123