xe1205 Semtech Corporation, xe1205 Datasheet - Page 11

• Manufacturer Part Number: xe1205
• Description: Low-power, High Link Budget Integrated Uhf Transceiver
• Manufacturer: Semtech Corporation

number of bits used for comparison is defined in the RXParam_Psize(1:0) register and the number of tolerated errors for
the pattern recognition is defined in the RXParam_Ptol(1:0) register. Figure 4, illustrates the pattern matching process.
Note: The pattern recognizer is available only if the bit synchronizer is enabled.
5.2.3.4
This function provides a Received Signal Strength Indication based on the signal level at the output of the base-band
filter. To activate this function, the bit RXParam_RSSI must be set to
stored in register RXParam_RSSI_OUT(1:0) and may be read through the serial control interface. The meaning of this
status information is given in the table below, where V
when the receiver is operated in mode A. The thresholds VTHRi are at the output of the base-band filter divided by the
gain between the input of the receiver and this output. When operated in mode B, equivalent VTHRi thresholds are
shifted 15dBm higher.
The operating range of the RSSI measurement may be changed by programming the RXParam_RSSI_range bit; in this
way two ranges with three VTHRi values may be selected. An additional way to increase RSSI operating range is to
combine modes A and B thresholds. One could then cover input signals ranging from -110dBm (VTHR1, low range,
mode A) up to -70dBm (VTHR3, high range, mode B)
The time diagram of an RSSI measurement is given in Figure 5. When the RSSI function has been activated the signal
strength is periodically measured and the result is stored in RSSI_out_int; this result is transferred to the register
RXParam_RSSI_out(1:0) each time this register is read via the SPI interface. TS_RSSI is the wake-up time required
after the function has been activated to get a valid result and its value is given in section 4.2.2. TS_RSSIM is the period
between two successive measurements and its value depends on the selected frequency deviation (100 ms for Df > 20
kHz, 200 ms for 10 kHz < Df
kHz).
© Semtech 2007
DCLK
(NRZ)
DATA
PATTERN
RSSI in continuous mode
Reg_pattern[x]
Bit N-x =
RXPARAM_RSSI_out(1:0)
20 kHz, 300 ms for 7 kHz < Df
0 0
0 1
1 0
1 1
Reg_pattern[1]
Figure 4: Pattern matching operation.
Table 7: RSSI status description
Bit N-1 =
RFFIL
Reg_pattern[0]
Description
V
VTHR1 < V
VTHR2 < V
VTHR3 < V
RFFIL
11
is the differential amplitude of the equivalent input RF signal
Bit N =
10 kHz, 400 ms for 5 kHz < Df
£ VTHR1
RFFIL
RFFIL
RFFIL
. When activated, the 2-bit status information is
£ VTHR2
£ VTHR3
7 kHz, and 500 ms Df
XE1205
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