CC1020_12 Datasheet, PDF (59/96 Pages) Texas Instruments – Low-Power RF Transceiver for Narrowband Systems

application. By specifying the total
expected frequency accuracy in SmartRF^®
Studio together with data rate and
frequency separation, the software will
estimate the total bandwidth and compare
CC1020
to the available receiver channel filter
bandwidth. The software will report any
contradictions and a more accurate crystal
will be recommended if required.
XOSC_Q2
C4
XTAL
XOSC_Q1
C5
Figure 33. Crystal oscillator circuit
Item
C4
C5
C_L= 12 pF
6.8 pF
6.8 pF
C_L= 16 pF
15 pF
15 pF
C_L= 22 pF
27 pF
27 pF
Table 28. Crystal oscillator component values
20. Built-in Test Pattern Generator
The CC1020 has a built-in test pattern
generator that generates a PN9 pseudo
random sequence. The PN9_ENABLE bit
in the MODEM register enables the PN9
generator. A transition on the DIO pin is
required after enabling the PN9 pseudo
random sequence.
The PN9 pseudo random sequence is
defined by the polynomial x⁹ + x⁵ + 1.
The PN9 sequence is ‘XOR’ed with the
DIO signal in both TX and RX mode as
shown in Figure 34. Hence, by transmitting
only zeros (DIO = 0), the BER (Bit Error
Rate) can be tested by counting the
number of received ones. Note that the 9
first received bits should be discarded in
this case. Also note that one bit error will
generate 3 received ones.
Transmitting only ones (DIO = 1), the BER
can be tested by counting the number of
received zeroes.
The PN9 generator can also be used for
transmission of ‘real-life’ data when
measuring narrowband ACP (Adjacent
Channel Power), modulation bandwidth or
occupied bandwidth.
SWRS046E
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