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XE1203F View Datasheet(PDF) - Semtech Corporation

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XE1203F Datasheet PDF : 36 Pages
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XE1203F
4.1.6 Pattern recognition block
When in receiver mode, this feature is activated by setting RTParam_Pattern Configuration Register bit high. The
demodulated data signal is compared with a pattern stored in the PATParam_Pattern Configuration Register. The
PATTERN output pin is driven by the output of this comparator and is synchronized by DCLK. It is set to high when
a matching condition is detected, otherwise set to low. The PATTERN output is updated at the rising edge of DCLK.
The number of bits used for comparison is defined in the ADParam_Psize Configuration Register and the number of
tolerated errors for the pattern recognition is defined in the ADParam_Ptol register. Figure 4, below, illustrates the
pattern matching process.
Figure 4: Pattern Matching Operation.
4.1.7 RSSI
When enabled, this function provides a Received Signal Strength Indication based on the signal at the output of the
base-band filter. To enable the RSSI function, the RTParam_RSSI Configuration Register bit should be set to “1”.
When enabled, the status of the RSSI in the DataOut_RSSI register is a 2-bit word which can be read via the serial
control interface. The content of the register is defined in Table 5, below, where VRFFIL is the differential amplitude
equivalent to the RF input signal with the receiver operated in A-mode. The thresholds, VTH are the equivalent of the
signal at the output of the base-band filter stage, divided by the signal gain.
DataOut_RSSI
00
01
10
11
Description
VRFFIL VTHR1
VTHR1 < VRFFIL VTHR2
VTHR2 < VRFFIL VTHR3
VTHR3 < VRFFIL
Table 5 RSSI status description
Two possible ranges, each having a set of three VTH threshold values, VTHR1, VTHR2, and VTHR3 (see 3.2.2 for
actual values), are selected with the RTParam_RSSIR Configuration Register bit. They provide an overall RSSI
range of typically 25 dB.
The timing diagram of an RSSI measurement is illustrated in the Figure 5 below. When the RSSI function has been
activated, the signal strength is periodically measured and the result is stored in the register DataOut_RSSI each
time this DataOut_RSSI register is read via the 3-wire serial interface. Note that TS_RS is the wake-up time
required after the function has been enabled to ensure that a valid reading of RSSI is obtained.
© Semtech 2007
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