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CC1000-RTB1

Part # CC1000-RTB1
Description RF Transceiver FSK 3V 28-PinTSSOP Tube - Rail/Tube
Category IC
Availability In Stock
Qty 143
Qty Price
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40 - 77 $7.13604
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117 + $5.91066
Manufacturer Available Qty
Texas Instruments
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Technical Document


DISCLAIMER: The information provided herein is solely for informational purposes. Customers must be aware of the suitability of this product for their application, and consider that variable factors such as Manufacturer, Product Category, Date Codes, Pictures and Descriptions may differ from available inventory.

CC1000
SWRS048A Page 19 of 55
12. Bit synchroniser and data decision
Sampler
Average
filter
Data
filter
Decimator
Frequency
detector
Data slicer
comparator
Figure 11. Demodulator block diagram
A block diagram of the digital demodulator
is shown in Figure 11. The IF signal is
sampled and its instantaneous frequency
is detected. The result is decimated and
filtered. In the data slicer the data filter
output is compared to the average filter
output to generate the data output.
The averaging filter is used to find the
average value of the incoming data. While
the averaging filter is running and
acquiring samples, it is important that the
number of high and low bits received is
equal (e.g. Manchester code or a
balanced preamble).
Therefore all modes, also synchronous
NRZ mode, need a DC balanced
preamble for the internal data slicer to
acquire correct comparison level from the
averaging filter. The suggested preamble
is a ‘010101…’ bit pattern. The same bit
pattern should also be used in Manchester
mode, giving a ‘011001100110…chip
pattern. This is necessary for the bit
synchronizer to synchronize correctly.
The averaging filter must be locked before
any NRZ data can be received. If the
averaging filter is locked
(MODEM1.LOCK_AVG_MODE=’1’), the
acquired value will be kept also after
Power Down or Transmit mode. After a
modem reset
(MODEM1.MODEM_RESET_N), or a
main reset (using any of the standard
reset sources), the averaging filter is reset.
In a polled receiver system the automatic
locking can be used. This is illustrated in
Figure 12. If the receiver is operated
continuously and searching for a
preamble, the averaging filter should be
locked manually as soon as the preamble
is detected. This is shown in Figure 13. If
the data is Manchester coded there is no
need to lock the averaging filter
(MODEM1.LOCK_AVG_IN=’0’), as shown
in Figure 14.
The minimum length of the preamble
depends on the acquisition mode selected
and the settling time. Table 4 gives the
minimum recommended number of chips
for the preamble in NRZ and UART
modes. In this context ‘chips’ refer to the
data coding. Using Manchester coding
every bit consists of two ‘chips’. For
Manchester mode the minimum
recommended number of chips is shown
in Table 5.
CC1000
SWRS048A Page 20 of 55
Manual Lock Automatic Lock Settling
MODEM1.
SETTLING
(1:0)
NRZ mode
MODEM1.LOCK_
AVG_MODE
=’1’
MODEM1.LOCK_
AVG_IN
=’0’=’1’**
UART mode
MODEM1.LOCK_
AVG_MODE
=’1’
MODEM1.LOCK_
AVG_IN
=’0’=’1’**
NRZ mode
MODEM1.LOCK_
AVG_MODE
=’0’
MODEM1.LOCK_
AVG_IN
=’X’***
UART mode
MODEM1.LOCK_
AVG_MODE
=’0’
MODEM1.LOCK_
AVG_IN
=’X’***
00 14 11 16 16
01 25 22 32 32
10 46 43 64 64
11 89 86 128 128
Notes:
** The averaging filter is locked when
MODEM1.LOCK_AVG_IN
is set to 1
*** X = Do not care. The timer for the automatic lock is started when RX mode is set in the
RFMAIN
register
Also please note that in addition to the number of bits required to lock the filter, you need to add the
number of bits needed for the preamble detector. See the next section for more information.
Table 4. Minimum preamble bits for locking the averaging filter, NRZ and UART mode
Settling
MODEM1.
SETTLING
(1:0)
Free-running
Manchester mode
MODEM1.LOCK_
AVG_MODE
=’1’
MODEM1.LOCK_
AVG_IN
=’0’
00 23
01 34
10 55
11 98
Table 5. Minimum number preamble chips for averaging filter, Manchester mode
CC1000
SWRS048A Page 21 of 55
Preamble NRZ data
Data package to be received
RX
Noise
RXPD
Averaging filter
free-running / not used
Automatically locked after a short period depending on “SETTLING”
Noise
Averaging filter locked
Preamble NRZ data
Data package to be received
RX
Noise
RXPD
Averaging filter
free-running / not used
Automatically locked after a short period depending on “SETTLING”
Noise
Averaging filter locked
Figure 12. Automatic locking of the averaging filter
Preamble NRZ data
Data package to be received
RX
Noise
PD
Averaging filter free-running
Manually locked after preamble is detected
Noise
Averaging filter locked
Preamble NRZ data
Data package to be received
RX
Noise
PD
Averaging filter free-running
Manually locked after preamble is detected
Noise
Averaging filter locked
Figure 13. Manual locking of the averaging filter
Preamble Manchester encoded data
Data package to be received
RX
Noise
PD
Averaging filter always free-running
NoisePreamble Manchester encoded data
Data package to be received
RX
Noise
PD
Averaging filter always free-running
Noise
Figure 14. Free-running averaging filter
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